
589 





Ml ^M^i> 



tLEMENTARY LESSONS 



IN THE 



PHYSICS OF AGRICULTURE 



BY 

pROFKftsoR or AfreicrrL.TrEAL Phtsjos ik the 
Fkiverstty of Wroonsix. 



flBU^HKi' ^^ 'HI ^L iflin. 






Copyright, 1891 and 1894, 

BY 

F. H. KING. 



Democrat Printing Co.. Madison 



T 



PREFACE. 

HE lack of literature relating to the physics of ag- 
riculture in any form available for class instruction 
has led to the preparation of these lessons to meet the 
immediate needs of our Short Course students. They 
are intended simply as a temporary expedient to be 
used until time shall permit the preparation of a suit- 
able text-book on the Physics of Agriculture. 

The Articles on Farm Drainage and The Construc- 
tion and Ventilation of Farm Buildings were prepared 
for other purposes, but are here appended to make 
them available for reference. 
Madison, Wis. 



CONTENTS. 

Page. 

Introduction, ------- 3 

Elements of Machines, ----- 16 

Strength of Materials, - - - - - - 38 

Fluids, -------- 46 

Heat, - - - - - - - - - 63 

Protection Against Lightning, - . - - 79 

Soil Physics, - - - - - - - 84 

Tillage, -------- 116 

Implements of Tillage, ------ 127 

Farm Drainage, ------- 142 

Construction and Ventilation of Farm Buildings, - - 157 

Table of Relative Humidities, - - - - 178 

Index, -------- 180 



INTRODUCTORY. 



1. Physical and Chemical Clianges. — When trees are 
cut into stove wood or cut into dust with the saw, the 
pieces which remain are wood still and such changes are 
2)hy steal ; but when the wood is placed in the stove and 
burned changes take place which destroy the wood, as such, 
and these are chemical changes. When a lump of sugar is 
dissolved in water tho sugar is sugar still and may be re- 
covered as such by evaporating the water, and the change 
is Q, physical OYiQ] but when yeast and "mother of vinegar" 
are added to the sweetened water and allowed to stand the 
sugar is transformed, alcohol and then vinegar appear 
in its stead, and the changes are chemical ones. The fall 
of rain and snow to the ground, the flowing of streams to 
the sea and the evaporation and return of the water to the 
land again are all physical changes. The operations of 
tillage, of drainage, the cutting and handling of farm prod- 
uce and the making of butter are physical processes. The 
running of farm machinery and the construction of farm 
buildings involve the application of jyhf/sical rather than 
chemical laws. 

Write a list of five physical and five chemical changes. 

2. Matter and Force. — The physical universe, so far 
as we are able to comprehend it at present, appears to be 
made up of two classes of agencies, one of which is active 
and called force., while the other is passive, or acted upon, 
and named matter. AVater is matter, and gravity is the 
unseen force or agency which causes it to flow to the sea 
or to turn the water wheel; air is matter, but gravity is 
the force which moves it in the wind when it drives the 
ship or turns the wind -mill. Wood and oxygen are mat- 
ter, but chemical afiinity is the force which drives their 
molecules into collision producing the intense heat and 
light of the fire. 

3. Kinds of Matter. — Chemistry at present distin- 
guishes about seventy kinds of matter which are known 
as elements or elementary substances; oxygen, hydrogen, 



nitrogen, carbon, iron, sulphur and phosphorus are seven 
of these. Water is not one of the elements, for it can be 
decomposed and shown to consist of oxygen and hydrogen. 
Sugar is not an element, but is made up of carbon, oxygen 
and hydrogen. 

4. Constitution of Matter. — Each and every body or 
mass of elementary substance, is composed of large num- 
bers of minute units or individuals named atoms, which 
various lines of experiment, observation and reasoning 
show to be constant in weight and properties, so far as 
we know them; and it is in consequence of this constancy 
of weight and properties that chemistry is able to analyze 
the various substances and tell us their composition. 

The atoms of which all bodies are composed rarely exist 
alone; they are bound into tiny clusters called molecules. 
Some of these molecules are made up of two atoms, like those 
of common salt containing one of chlorine and one of so- 
dium; other molecules contain three atoms, like those of 
water, two of hydrogen and one of oxygen ; molecules of cane 
sugar contain forty-five atoms, twelve of carbon, twenty- 
two of hydrogen and eleven of oxygen. Commercial ana- 
line violet possesses molecules of fifty-seven atoms of five 
different kinds, and there are other atom clusters or mole- 
cules more complex than these. 

5. The Size of Molecules. — The size of molecules is 
almost inconceivably minute. Sir William Thompson com- 
putes the number of molecules in a cubic inch of any per- 
fect gas having a temperature of 32" F. and under a pres- 
sure of thirty inches of mercury, to be 10-^ or ten sextill- 
ions. 

We have many strong proofs of the extremely minute 
size of molecules. If a grain of strychnine be dissolved in 
one million grains of water, and if we place one grain of 
the water containing the strychnine in the mouth, its bit- 
ter taste is recognizable, and yet the volume of a grain of 
strychnine is only about ^^5 of a cubic inch. A cubic inch 
of analine violet will impart its purple color to more than 
eight million three hundred and eighty-four thousand cubic 
feet of water. Nobert succeeded in engraving parallel 
lines on glass at the rate of more then one hundred thou- 
sand to the inch, and hence the point of his diamond must 
have been much thinner than this, and the diameters of 
the molecules which composed it smaller still. 



The fact that musk and other perfumes keep the air of 
large apartments so charged with their molecules that we 
are able to detect them in spite of the fact that the air is 
constantly changing and the loss in weight of the per- 
fume is extremely small indeed, is still another striking 
proof of the minuteness of molecules, and, at the same 
time, of our ability to recognize them. 

6. Properties of Molecules. — Molecules possess mag- 
nitude and weight and are divisible into atoms. When- 
ever a chemical change takes place existing molecules are 
transformed into new ones of a different kind and chem- 
istry, as a science, deals with these changes, while physics 
deals' with the molecules and groups of them. 

7 Structure of Bodies. — The bodies or masses of 
matter with which we are familiar are always composed of 
molecules but these molecules are believed to be not in 
contact with one another. 

If a quantity of salt be placed in a vessel and then water 
added so that the combined volume before solution fills the 
vessel, when the salt dissolves the volume will be found to 

be less 

The fact that bodies change their volume with changes of 
pressure and of temperature also indicates that the mole- 
cules which compose them are not in contact. 

The mercury in a thermometer, for example, fills the bulb 
at 212^ F. and a certain portion of the stem also, but as the 
temperature falls the mercury in the stem withdraws into 
the bulb and yet the capacity of the bulb diminishes by 
contraction at the same time, and this could not take place 
were there not room in the bulb not occupied by the mole- 
cules of mercury. 

8. Molecules of Bodies Not at Rest. — Not only are 
the molecules which constitute the various bodies around us 
not in contact with one another, but a large number of facts 
and observations indicate that they are not relatively at 
rest. If a solution of sugar or salt be placed in the bot- 
tom of a vessel and covered with water the molecules of 
sugar and salt travel upward and those of the water down- 
ward until, finally, a uniform mixture of the two liquids 
has resulted. The same fact is also observed where two 
gases are brought si. contact — diffusion takes place. So. 
if a solid lump of sugar or of salt be placed in water, the 



molecules travel away and disperse themselves through the 
whole mass. The molecules of fragrance 'from fruits and 
flowers are constantly traveling away from their respect- 
ive places of origin. Molecules of camphor leave the solid 
lump and travel through the surrounding air, and snow 
disappears into the atmosphere without melting on the 
coldest of winter days. 

The pressure which steam exerts upon the • head of the 
piston when driving the engine is regarded as due to the 
collision of the molecules against its face; and the pressure 
exerted by all gases is explained in the same way. The 
temperature of bodies is also an expression of the degree 
of molecular agitation within them. When we place the 
fino-ers upon a warm body the motion of its molecules is 
communicated to the molecules of the cuticle, and this in 
turn to the nerve endings,, and onward through the nerves 
to the nerve centers in the brain, giving rise to the sen- 
sations denominated hot, warm, cool or cold. 

The mean distance traveled without collision by a mole- 
cule of hydrogen at ordinary temperature and pressure is 
computed" by Crooks at jtj^tjo mm., or ^^^Vfo i"-, while the 
velocity is at the rate of about six thousand feet per sec- 
ond. The heavier the molecules are the slower they move, 
the rates being inversely as the square roots of their 
w^eights. Thus the oxygen molecule, being sixteen times 
as heavy as the hydrogen molecule, moves under like con- 
ditions, only one-fourth as rapidly. 

If it is difficult to think of a body like a horse-shoe or a 
hammer maintaining its form when its molecules are 
neither in contact nor relatively at rest, it may be helpful 
to turn to the solar system, consisting of the sun, planets, 
satellites and asteroids, together with comets and meteors, 
all of which are in constant and rapid motion, separated 
by immense distances, and yet as a whole constituting one 
great body, maintaining a definite form and size as it 
travels through space. 

9. Kinds of Force.— The falling of leaves, of rain-drops 
and of unsupported bodies generally, is a constant re- 
minder of an influence which the earth, as a whole, exerts 
upon bodies at its surface. The strength and rigidity of 
solids as compared with fluids; the union of two boards 
by means of glue; the rise of oil in a lamp-wick, and its 



destruction by burning, with the appearance of heat and 
light, all convince us of influences of some sort which the 
molecules of bodies exert upon one another. 

It has been customary to speak of these influences as due 
to the action of different kinds of force, and they have re- 
ceived distinctive names. 

10. (gravitation is the action which any one molecule 
exerts upon every other molecule, tending to draw them to- 
gether no matter how great the distance may be between 
them. The intensity of this attraction is directly propor- 
tional to the mass and inversely proportional to the dis- 
tance between the molecules. 

The weight of a load of hay or of a bushel of wheat is 
the sum of the attractions of every molecule of the earth 
upon all the molecules of the load of hay or bushel of 
wheat. 

11. Molecular Forces. — When moler-ules are brought 
very close to one another, so that the distances between 
them become inappreciable, their tendency to come together 
or their resistance to separation are spoken of as due to 
molecular attraction, and three varieties are desio-nated, 
viz., cohesion, adhesion and chemical afflnity. 

12. Cohesion. — When water is cooled below 32^ F. the 
rate of molecular motion and the mean distance between 
the molecules so diminishes that the force of cohesion be- 
gins to bring them into new relations and to bind them 
more firmly together, so that a solid body results. The 
same force comes strongly into action when melted iron, 
copper or other metal changes from a liquid to a solid 
state. 

When finely ground graphite is subjected to extreme 
pressure in moulds, after having been first thoroughly 
cleaned, the molecules of the separate fragments are brought 
so closely together that they unite into solid cakes, from 
which the leads of pencils are sawed. Where molecules of 
the same kind are thus bound together the acting force is 
named cohesion. 

13. Adhesion. — When the smooth, plane surfaces of 
two pieces of wood are coated with a paste of glue and 
brought firmly together they are held very securely when 
dry. In this case the action between the molecules of glue 
and the molecules of wood on either side serves to make a 
single body of the three. The action seems to be essen- 



tially the same as that of cohesion, but because it occurs 
between molecules of different kinds the term adhesion is 
used to designate this distinction. The coating of walls 
with whitewash, paint, varnish and the like are other 
manifestations of the same force. 

14. Chemical Affinity. — When the temperature of 
wood is raised to a sufficiently high point in the presence 
of air an action occurs between the molecules of wood and 
those of the oxygen of the air, which results in the com- 
plete breaking dow^n of both sets of molecules and the 
formation of new^ ones of entirely different kinds in their 
stead. This sort of molecular action, as in the case of ad- 
hesion and cohesion, takes place only across insensible dis- 
tances, and the agency which brings it about is named the 
force of chemical affinity. The rusting of iron, the heat- 
ing of a manure pile or of a silo, the souring of milk and 
the processes of digestion are all phenomena in which this 
force is operating to form new molecules from old ones. 

1 5. States of Substances. — It is common to speak of 
substances as existing, under different conditions, in a 
solid, liquid or gaseous state. A critical study of these 
states, however, shows that no absolute distinction exists 
between them, and that, by insensible gradations, one 
state may shade into another. The substance water we 
know as solid ice, liquid water and gaseous steam. Iron 
at ordinary temperatures we think of as a solid, but as its 
temperature is raised it gradually becomes more and more 
soft until it passes by insensible shades into the condition 
of a true liquid. 

The ideal solid is a body which, if brought under a force 
w^hich tends to change its form, responds, if at all, to the 
force, and then remains unchanged so long as that condi- 
tion of stress may exist. The steel spring, when loaded, 
chaneces its form, and then remains constant until the load 
is removed, or rather appears to when rough measurements 
only are applied as a test; but if more than a certain load, 
is applied, the form keeps changing so long as the load acts. 

The ideal liquid is the body which constantly changes its 
form whenever a force is made to act more intensely upon 
one jDortion of it than upon another. We think of water as 
a perfect fluid, and yet a comparatively heavy load may be 
placed upon a drop of water resting upon a dusty surface 
without its changing form, except a definite amount at first. 



9 

On the other haud, we think of sealing-wax as a solid, and 
yet if a bullet be placed upon it, it will, by its own weight, 
gradually sink through it. But jelly, even when rather 
soft, will keep its form under the same load which will 
sink through the sealing-wax; the sealing-wax conforms to 
the law of liquids and the jelly to that of solids. 

In the gaseims state the molecules of the substance have 
attained so large a range of motion that the molecular at- 
tractions appear entirely overcome, and the molecules con- 
tinually separate from one another unless some confining 
surface or wall prevents them. No vessel can be half filled 
with a gas as it can with a solid or a liquid, for the mole- 
cules travel to and fro from side to side or from top to 
bottom, thus occupying the whole space, no matter whether 
the number of molecules be ten or ten millions. 

16. Work. — When a force, like that exerted by a horse, 
acts upon a quantity of matter and changes its position in 
any direction, tcork is done, and the amount of it is meas- 
ured by the product of the force and the space through 
which the mass has been moved. 

Work=Force x Space. 

If a horse exerts an average tension of twenty pounds 
through the whippletree upon the carriage and moves it 
through ten thousand feet the work done is 

20 lbs. X 10,000 --=200,000 foot-pounds, 

meaning the equivalent of two hundred thousand pounds 
lifted one foot in opposition to gravity. » 

So if the horse exerts a tension of one hundred pounds in 
raising a forkful of hay and carries it through a height of 
forty feet the work done is 

100 lbs. x 40^4000 ft.-lbs. 

Simple pressure is not work. The load must move be- 
fore work is done. The man who stands still under a sack 
of grain does no work on the load he holds. 

The mean rate of doing work is the whole work done di- 
vided by the time required to do it, and 550 foot-pounds 
per second is called a Horse- power by engineers. This, 
however, is more work than the average horse can do, this 
being estimated by General Morin at 26,150 foot-pound« 
per minute or 435.8 foot-pounds per second. 



10 

A laborer lifting dirt with a spade has been found able 
to do 470 foot-pounds per minute, and on a tread power, 
raisinor his own weight, 4,230 foot-pounds per minute; the 
first being .018 of an animal horse-power and the latter 
.16 or a little less than one-sixth. 

17. Energy. — Energy is the ability of a moving body 
to do work. If a twenty-pound weight, suspended by a 
cord, be drawn to one side and then allowed to fall, it will 
rise on the opposite side of the line of rest to a height 
nearly equal to that from which it fell. This height would 
exactly equal that from which it falls if the air and the 
suspending cord offered no resistance. Here the moving- 
weight, on reaching its lowest level, has acquired an 
amount of energy equal to that which has been expended 
in raising the weight to the point from which it fell. 

When a hammer is brought to rest on the head of a nail 
it is the energy of the moving hammer which does the 
work of forcing the nail into the wood. 

The wind blowing through the wind-mill has its velocity 
reduced, and so much of its energy is transformed into 
motion of revolution in the wheel. The same is true of 
water in flowing through a water-wheel, the water loses 
energy by imparting it to the whesl. 

When the spring of a clock or watch is wound up its 
molecules are drawn out of positions of rest, as with the 
weight referred to, and in falling back to their positions 
of rest again their energy is imparted to the train of 
wheels to which the spring is attached. 

18. Efiergy anil Matter Indestructible.— No discov- 
ery of modern science is more fundamental and far-reach- 
ing than that of the indestructibility of both matter and 
energy, and equally fundamental is the other fact that 
neither of them can be created. 

One form of energy can be transformed into another 
form and one kind of substance can be decomposed and 
others made from the components, but iii these transfor- 
mations there is never either annihilation or creation. 
The few bushels of ashes left from the winter's supply of 
coal or wood seem to point to a destruction of matter, but 
their weight added to the weight of the products which 
escaped through the chimney is actually greater than that 
of the original fuel, for oxygen from the air has united 
with it. So when the energy of eight or ten horses is be- 



11 

iog expended in the threshing of grain it looks as though 
energy were being annihilated, but it is simply chano-ed 
into heat, sound and energy of position, not lost. We 
appear to realize in the waste products of domestic ani- 
mals and the increase of their bodies a very much smaller 
weight of matter than they have consumed, but this is be- 
cause so large a weight passes off in an invisible form 
through the skin and lungs. Something is nevet\ so far as 
we know, reduced to nothing : neither is soynething created 
from notliing. 

19. Machines not Generators of Energy. — When, 
through the aid of a machine, a man or a horse is able to 
move a load which he could not otherw^ise handle, the ma- 
chine is not a source of energy, it is simply a device which 
enables their energy to be transmitted and used more ad- 
vantageously; but there is always some loss in the ma- 
chine, no matter what that machine may be. Some energy 
is required to overcome the necessary friction of the mov- 
ing parts of the machine so that the useful work accom- 
plished never quite equals the energy expended. 

20. Inertia of Matter. — Newton's first law of motion 
may be stated as follows : Every body tends to persevere in 
its state of rest or of uniform motion in a straight line un- 
less acted upon by some external force, or briefly, matter has 
inertia. There are many unmistakable illustrations of this 
law. The sudden starting of a wagon tends to throw a 
standing person backward because his feet take on the mo- 
tion first and are carried out from under him. In beating 
a carpet the carpet is driven forward away from the dust. 
In driving a nail the suddenness of the blow forces the 
wood aside and in front of the nail before the motion can 
spread to the surrounding wrod. 

When a horse, in rapid motion, suddenly turns a corner, 
the rider must lean in the direction of turning until his. 
tendency to fall exacily balances his tendency to move on 
in a straight line. It is the principle of inertia which 
enables the rider to sit securely on the bicycle while it is 
in motion ; the same principle explains the standing of the 
top while in motion, and the constant parallelism of the 
earth's axis during its revolutif^n about the sun. The 
rider on the bicycle is moving rapidly in one direction, and 
for him to fall either to the right or the left would require 
him to change his direction of motion at a right angle. 



12 



which is the same thing as trying to turn a corner when 
at full speed — a thing practically impossible. It is this 
law of inertia which makes it possible for the penman to 
make his smooth curves only by rapid movements of the 
hand. 

21. Centrifugal Force. — Centrifugal force, so called, 
is another manifestation of the law of inertia. The stone 
twirled about the head with a string, because of its tend- 
ency to move always in a straight line, exerts a constant 
tension upon the string, and if the rate of motion is sreat 
enough the string will be broken. 

It is this manifestation of inertia in circular motion 
which lies at the foundation of all rotary forms of cream- 
separators and extractors and of several forms of fat-tests 
for milk. 

In the Babcock and Beimling "milk-tests" the rapid 
revolution of the bottles which 
contain the fat to be sepa- 
rated from the liquid with which 
it is mixed, throws the heavy 
liquid to the bottom of the bot- 
tles, which reacts upon the fat, 
forcing it toward the center of 
the circle, where the velocity 
is least. The fat, like the heav- 
ier liquid, in consequence of its 
own inertia, tends to go to Ihe 
bottom of the bottles also and 
is simply prevented from doing 
so by the greater inertia of the 
heavier liquid. 

22 The Gravity Metliod of Creaming. — To under- 
stand the reason for the more rapid and perfect separation 
of cream by the centrifugal methods over the simple gravity 
methods we need to get first the principle of creaming by 
gravity. 

It is this: If a block whose weight is but one-half that 
of an equal volume of water be immersed in water it 
will be lifted by a force equal to the difference between the 
weight of the block and that of an equal volume of water, 
as shown in Fig. 1. 

Regarding the water of the vessel divided into cubes ex- 
actly equal in volume to the bicck of wood, and the block 




Fig. 1, 



13 

just half as heavy as an equal volume of water, then the 
weight of column A equals 

2 + 2+1=5, 

while the weight of column B is 

2+2 + 2=6. 

Now, as column B exerts a pressure upward on the column 
A equal to its own weight, the block in column A must be 
pushed upward by a force equal to the difference in the 
weight of the two columns, or of 

6-5=1. 
A comparison of columns B and C will show that it 
makes no difference where the block is placed in the liquid, 
the force which tends to lift it to the surface is always the 
same. If the attraction of the earth were just twice as 
strong as it is then the cubes of water and the block in 
column A would weigh 

4+4 + 2 = 10, 
and the cubes of water in column B would weigh 

4 + 4+4=12, 

and the lifting force on the block would be 

12-10=2, ' 

or just twice what it now is; so if the force of gravity 
were made one hundred times what it now is, the lifting 
force acting upon the immersed block would be increased 
one hundred fold. 

23. Centrifugal Creaming.— The centrifugal methods 
of creaming are applications of the same principle as the 
gravity methods, the only difference being in the substitu- 
tion of a stronger force in the place of gravity, and by so 
doing of shortening the time and securing a more complete 
separation. This is done by transforming the energy of 
an engine or of some other form of motion into the energy 
of rapid rotation in the milk, giving rise to a strong out- 
ward pressure, which acts exactly as gravity does in the 
old method of creaming. 

24. To Compute the Centrifugal Force.— The 
strength of centrifugal force in a milk separator may be 
computed as follows : 

weight of milk x (velocity i n feet per sec. , '• 
Centrifugal Force = ^radius x 32.2. 



14 

Suppose the mean diameter of the circle through which 
one pound of milk is made to revolve is ten inches, and 
that the centrifuge is given seven thousand revolutions per 
minute. In this case the 

10 X 3.1116x7000 
Velocity = j^o X GO —305.1, 

., , .„ , „ lib. X (305.4). „_^ 
then centrifugal force= r ^r^-; — ^^=9GoO 

and this means that the creaming force would be six thou 
sand nine hundred and fifty times as great as by the old 
gravity method. 

25. Strength of the Creaming" Force. — Since the 
mean specific gravity of milk fat at 85" to 00° F. is about 
.91 and that of milk serum 1.031, the creaming force must 
be the difference between the two specific gravities, as 
shown in ti2, or 

1.034-.91=.124: 

that is, if a ball of butter-fat weighing .91 pounds were 
placed in milk serum, the lifting force of gravity upon it 
would be .124 pounds, but if placed in milk serum in the 
centrifuge under the conditions of 24 the creaming force 
would be 

(5950 X .124=861.8 lbs. 

This enormous creaming force seems unnecessarily large, 
and so it would be if the fat globules were large enough to 
weigh .91 of a pound each, as in the problem assumed, for 
then creaming by the gravity method would be practically 
instantaneous, whereas, under existing conditions, it re- 
quires about twelve hours. 

The actual diameter of the average fat globule in milk 

is not far from __ _ of an inch, while a sphere of butter- 
5000 ^ 

fat weighing one pound would have a diameter of about 

3.87 inches. 

Now as the volumes of spheres are to each other as the 

cubes of their diameters, the pound of fat should contain 

about seven trillion two hundred and forty-five billion of 

fat globules. But the surfaces of spheres are to each other 

as the squares of their diameters, and hence the surface of 

the pound sphere will contain the surface of the fat glob- 



15 

■ule about three hundred and seventy-four million four 
hundred and twenty-two thousand five hundred times; and 
this being true, the aggregate surface of the seven trillion 
two hundred and forty-five billion fat globules, whose ag- 
gregate volume equals that of the pound sphere, must be 

72450000f0000_ 

"374422500"-^^'^''^ 
times the surface of the pound sphere; and when we re- 
member that the friction increases with the surface, and 
that more force is required for rapid creaming than for 
slow, we can see that a much stronger creaming force is 
really needed. 

26. Storing Elierg-y.— In many forms of machinery 
where the work to be done, like that of sawing wood with 
a buzz saw. is not a steady draught upon the source of 
power, a fly-wheel, or its equivalent, is very useful in al- 
lowing the power generator to store energy when work is 
not being done and give it out again as needed. The wind- 
mill in pumping water, with most pumps, does work only 
half the time, ijind so there is often attached to the pump 
an air chamber which acts like a sprirg in which the mill 
stores energy by compressing air which is given out dur- 
ing the reverse stroke. A constant stream is thus main- 
tained and the pump enabled to be worked with lighter 
winds than would otherwise be possible. 

In the animal mechanism the walls of the arteries are 
elastic and act like springs. They are stretched by the 
powerful, quick contractions of the heart, and then, while 
the heart is resting, the blood is forced on by the steady 
return of the stretched arterial walls, and continuous cur- 
rents of blood are thus moving through the tissues of the 
body. 

27. Momentum.— When a body weighing ten is moving 
with a velocity of ten, the quantity of motion is 

10 X 10=100, 
and this is called its mcimrdvm. If the mass of the body 
is one thousand and its velocity is five, then 

1,000x5=5,000, 
the quantity of motion, or momentum, of that body. So a 
body having a mass of five and a velocity of one hundred 
has the same momentum as a body weighing ten, having 
a velocity of fifty, for 

5 X 100=500 and 50 x 10=500. 



ELEMENTS OF MACHINES. 



28. The Meehaiiical Powers.— The simple machines 
known by the names lecer, wheel and axle, inclined plane, 
screw, wedge and knee find an explanation of their action in 
the fact that they simply transmit motion with an altered 
velocity or direction, the quantity remaining always the 
same, except as it is diminished more or less by the fric- 
tion and weight of the parts of the machine itself. 

29. The Lever. — The lever may be any bar sufficiently 
rio-id to retain its form when forces are applied to it. The 
terms used in speaking of the action are the fidci-um, power 
ar?n an(\ weight-arm: these are represented in Fig. 2. 

Tourer ^f^ ^ Arnv^ 

Ju\craitt 

There ai'e three classes of levers, named First, Second 
and Third, according to the relative positions of the ful- 
crum to the points where the power and weight are ap- 
plied : these are represented in Fig. 3. 







/5> 3 

The mechanical advantage of the crow-bar, in moving a 
heavy object, lies in the fact that it enables the muscles 
to generate energy at their usual relatively rapid rate, 
and transform it into so slow^ a velocity in the load to be 
moved that a heavy weight is required to balance the 
smaller more rapidly acting power. Suppose w^e have a 
crow-bar sixty inches long, and the fulcrum is placed at 
two inches from one end when it is being used as a lever 
of the first class. In this case, as shown in Fig. 4, 



17 



both the power and the weight travel on the circumferences 
of circles, the power circumference having a radius of fifty- 
eight inches, and the weight circumference having a radius 
of two inches. 




. Now the circumferences of these two circles have the same 
relative lengths as their radii do, and since the lever does 
not bend, the weight can have a velocity only ^\ or ^V as 
great as that of the power, and since the power is ten and 
its velocity twenty-nine times that of the weight, its mo- 
iiientum must be 

10x29 = 290; 
and this being true, the weight, in order to just balance 
the power, must have mass enough so that, with a velocity 
of one the amount of motion shall exactly equal that of the 
power, and hence we have 

1x290 = 290, 
as the load which ten will balance on a lever acting as rep- 
resented. 




When the crow-bar is used as represented in Fig. 5, it 
becomes a lever of the second class, with the power-arm 
sixty inches long, while the weight arm is still two inches. 
In this case a power of thirty pounds will balance a load 
of nine hundred pounds. 



\^\-30 



iV.A »^ff 



P^f90(f 






When the power is applied to the lever between the weight 
and the fulcrum, as represented in Fig. 0, the case becomes 



18 



a lever of the third class, and a power of nine hundred be- 
comes necessary to move a load of thirty. 

The relation of power to weight in the case of any lever 
is expressed by the equation below, where P. equals power, 
W. equals weight, P. A. equals power- arm and W. A. 
weight -arm : 

P. xP. A. = W. X W. A. 

When any three terms in this equation are known the 
fourth may readily be found. 

How great a load may be moved by a power of thirty 
pounds acting on a lever having a power-arm of twenty 
and a weight-arm of three? 

P. xP. A.= W. X W. A. 

30 X 20 = W. X 3. 
600 = 3 W. 
W. = 200 1bs. 



30. The Two-horse Eveiier. — This is a lever of the 
second class where the whippletree clevis-pin acts as the 
fulcrum for each horse, the weight or load being carried 
by the center pin. As ordinarily constructed this instru- 
ment is designed to divide the work of moving the load 
equally between the two horses. This, however, is not 
done at all times unless the three holes lie in the same 
straight line. 




When the holes are bored as shown in Fiof. 7 the load is 
divided equally only when one horse is not behind the other. 



19 

The figure shows that when the near horse falls behind 
the other the effective length of his lever arm is dimin- 
ished more than is that of the off horse, and consequently 
he must pull a larger share of the load. 

When the holes are bored in the same straight line the 
possibility of this inequality is avoided, as shown in Fig. 
8, because the changes in the effective lengths of the lever 
arms are always equal no matter which horse falls behind. 
This latter form, although the best so far as dividing the 
labor evenly between the two horses, is rarely adopted in 
practice, owing chiefly to the possibility of more cheaply 
constructing the evener the other way. 




^ ^ 


\ 


> 




\ 


s 


s 


1 


y 



Where heavy loads are to be moved, like pulling stones 
or stumps, or hauling a load out of a rut or out of the mud, 
the second type of evener will always allow a matched 
team to pull a larger load, because the horse which hap- 
pens to be thrown behind, in attempting to start the load, 
is placed at a disadvantage and the other horse can only 
pull enough to hold his end against the one placed at 
a disadvantage. So, too, in doing heavy work, where 
one horse is naturally a little freer or stronger than the 
other, the tendency is always to throw more than half the 
work upon the slower or weaker horse. 

31. *'Oiviiig One Horse the Advantage."— The fre- 
quent practice, where the two horses of a team are not 
equally strong, of "giving one horse the advantage" is 
based upon the principle that the amomut of work done 



20 

by each horse is inversely proportional to the length of the 
lever arm upon which he works. Suppose it is desired to 
so modify an evener that three-eighths of the work will 
fall upon one horse and five-eighths upon the other. In 
this case the horse which is to do five-eighths of the work 
must have his end of the evener e-hortened until its length 
is just three-fifths as long as that of the horse which is to 
do three-eisfhths of the work. If the distance from 1 to 2 
in Fig. 8 is forty-eight inches, then in order to require 
the near horse to do five-eighths of the work the power- 
arm of his lever will be 

11 in.=38,4 inches. 

5 

S 

This is given by substituting the numerical values in 
the general equation of the lever. 

P. xP. A. = W. X W. A. 

By substituting, f x P. A. = 1 x 2i in. 

Whence, P. A. = -/ in. = 38.4 in. 

This length of 38.4 inches will be secured by setting the 
clevis 9.6 in. nearer the center. 

How far in must the clevis be set to give the other horse 
an advantage of one-eighth? of one- sixteenth? of one- 
thirty-second? 

Taking the first of these examples one horse must pull 
nine-seventeenths and the other eight-seventeenths of the 
whole load ; in the second case they draw respectively seven- 
teen-thirty-thirds and sixteen-thirty-thirds. 






(looep T ^ ,P w 

fT^ 76- ^ 1 

32. Platform Scales. — Levers are of-ten used in com- 
bination when it is desired to balance a very heavy load 
by a small weight, and such combinations are spoken of 
as compound levers. The various forms of platform scales 
are examples of such combinations. In the case of hay 
scales, four thousand to six thousand pounds are balanced 
or lifted by a few pounds. 

The principle by which such combinations of levers give 



21 

"these great mechanical advantages will be understood from 
Fig 9. 

If F. F. F. F. are fulcrums of the levers I, II, III, IV, 
and their power-arms are each ten while their weight-arms 
are each one, then a power of two pounds at P. will balance 
a load of twenty thousand pounds at W. This must be so, 
for two pounds at P. will cause lever IV to exert a pres- 
sure of twenty pounds upon the long arm of lever III, the 
twenty pounds pressure of lever III will cause a pressure - 
of two hundred pounds on lever II; lever II transmits a 
pressure of two thousand pounds to the end of lever I, and 
this pressure will sustain a load of twenty thousand pounds 
placed at W. 

For levers m combination the continued product of the 
power and power-arms is equal to the weight into the con- 
tinued product of the weight-arms. 

P. X P. Arms=W. x W. Arms, 
or, 2 X 10 X 10 X 10 x 10=20,000 x I x 1 x 1 x 1. 

In the platform scales the platform is supported at its 
four corners by bearings which rest upon four levers, the 
ends of which are joined by means of a vertical rod to the 
short end of the graduated scale beam. The accuracy and 
sensitiveness of such scales depend upon the exactness with 
which the lever arms are constructed and the delicacy and 
durability of the bearings and fulcrums which transmit 
the pressure to the levers. 

33. The Locomotion of Animals.— Most of the higher 
animals which travel by means of appendages to their 
bodies propel themselves with a system of levers which are 
operated by sets of very powerful muscles. 

The mechanism of muscles and their method of contrac- 
tion make it possible for them to move through only very 
small distances, and hence where considerable movements 
are to be executed the results are secured by attaching 
them to the short arms of levers. In the forearm, for ex- 
ample, the biceps muscle acts upon a lever whose power- 
arm is only one-sixth as long as the weight-arm, and 
hence when a weight of fifty pounds is held as represented 
in Fig. 10 the muscle must exert a tension of three hun- 
dred pounds. 

The triceps muscle which extends the forearm is a more 
powerful one than the biceps, and in order to accomplish 



22 



its much more rapid movements it works upon a relatively 
much shorter lever arm, the relative lengths of the two 
arms being about as one to twenty or twenty-four. Now 




it is possible for the triceps muscle to exert a force upon 

a spring-balance exceeding twenty-four pounds, and hence, 

since 

P. xP. A. = W. X A., 
we have P. x 1 = '24 x 20, 
and P. =^480; 

which proves that the triceps muscle can exert a tension 
of four hundred and eighty pounds. It is this powerful 
muscle acting upon the hammer which enables nails to be 
so readily driven. 




The great tension which some of the muscles of horses 
must exert in pulling heavy loads, acting as they do at the 
short ends of levers, is almost beyond belief. 



23 



a 



34. The Wheel and Axle.— With the lever only 
small amount of motion can be communicated to a body at 
once, further movements only being possible after revers- 
ing its action. The wheel and axle, represented in Fig. 
11, enable power to be applied continuously in one direc- 
tion to the load or resistance to be overcome. 

The relation of power to weight in this element of ma- 
chines is expressed by the equation. 

Power X Power-Radius = Weight x Weight-Radius, 

or, briefly, 

P. X P. R.= W. X W. R., 

and by substituting the numerical values given in Fig. 11 
we get 

10 X 10 = 1 X 100. 

The relation of power to weight may also be represented 
in terms of the diameters or circumferences of the wheel 
and axle, thus : 

P. X P. R.= W. X W. R. 

P. X P. Diam.= W. x W. Diam. 

P. X P. Cir.= W. X W. Cir. 

« 

This mechanical power has by far the most extended use 
of any in ma3hinery. 

35. Trains of Wheels and Axles.— Wherever a great 
rotary velocity is desired, as in the case of the wood saw, 
in the cylinder of a threshing machine, in the fan of a 
fanning mill, or in the much higher speed of centrifuges, 
several wheels and axles are joined in a train by means of 
belts, gears, or friction pulleys; such systems are analo- 
gous to compound levers. 

The relation of power to weight both in intensity of ac- 
tion and in relative velocities is expressed by these equa- 
tions : 

1. For intensity of action: 

Power X Continued product of P. R.= Weight x Continued 

product of W. R. 

P. X P. Radii =» W. x W. Radii. 

2. For velocity : 

P. X P. Velocity = W. x W. Velocity. 



24 

36. The Sweep Horse-power. — This machine is an ex- 
ample of a train of wheels and axles whereby the slow 
walk of the horses is converted into the extremely rapid 
rotation of the cylinder of the thresher, feed-cutter or feed- 
mill the sweeps to which the horses are attached consti- 
tuting radii of the first wheel in the train. Here the 
small amount of work required of the machines at any one 
instant makes a high speed of execution desirable. 

37. The High Speed of Centrifuges.— This is se- 
cured by a combination of wheels and axles connected with 
belts. Suppose the diameter of the fly-wheel of the engine 
is twenty- four inches and it makes two hundred and 
twenty revolutions per minute. If this is belted to a six- 
inch axle or pulley on the driving-shaft, then the number 
of revolutions made by the wheel on the driving-shaft will 

be 

220x-V=^880. 

If the shaft-pulley connecting with the axle of the inter- 
mediate pulley has a diameter of ten inches while the axle 
has a diameter of five inches, then the wheel of the inter- 
mediate pulley will make 

880x Y-l'<'60. 

revolutions, and if the wheel^of the intermediate pulley 
has a diameter of twelve inches while the axle of the cen- 
trifuge is three inches, then the centrifuge will make 

1760xV='7040. 

revolutions per minute. 

Change the diameter of a wheel or axle so as to give the 
centrifuge four thousand revolutions; six thousand revolu- 
tions; five thousand revolutions. 

38. Exertion of Great Power.— When the exertion 
of a great lifting force is required at the expense of speed, 
this may be done by reversing the action of a train of 
wheels such as is considered in 37. In tliat case, if the 
power were applied at the centrifuge and the work done at 
the other end of the series, a load would be lifted very 
slowly indeed, but its weight cculd be very great. 

39. The Inclined Plane.— This mechanical power is a 
rigid surface inclined to the line of the force or resistance 
which it is to overcome, and is represented in Fig. 12. 

When the power moves parallel with the length or face 



25 



of the plane, as in A, the relation of power to weight is 
given by the equation 

Power X Length of Plane= Weight x Height of Plane, 
or 200 X 15=600 x 5. 

But when the power moves in a line parallel with the base 
of the plane, as in B, then the relation of power to weight 
is given by the equation 

Power x Length of Base=- Weight x Height of Plane, 
or 20 X 10=40 x 5. 



iV^^O 




40. The Tread Power. — This method of transferring 
energy is a practical application of the inclined plane, and 
the amount Avhich can be transmitted by it depends upon 
the height of the plane as compared with its length. 

If the length of the tread is eight feet and it is given a 
slant of one foot in eight feet, then from the equation 
P. X Length^W. x Height 

we get, with two thousand four hundred pounds as the 
weight of two horses, 

R X 8=2400 X 1, 
whence P.=300 lbs., 
as the intensity of the power exerted, diminished, of course, 
by whatever friction there may be. 

What would be the power if the slant were made one foot 
in seven feet? one foot in six feet? one foot in five feet? 

41. Traction on Common Roads — The power re- 
quired to draw a wagon over common roads varies with the 
character and condition of the road. Experiments in Eng- 
land with a four-wheeled wagon have given the following 
results for level roads as indicated by a dynamometer : 

On cubical block pavement 28 to 44 lbs. per ton. 

On macadam road 55 to 67 lbs. per ton. 

On gravel road 12.3 lbs. per ton. 

On plank road 27 to 44 lbs. per ton. 

On common dirt roads 179 to 268 lbs. per ton. 

42. Traction Power of a Horse. — According to the 
most reliable data available at present, which is certainly 



26 

far short of what could be desired, a horse in good condi- 
tion, well fed, and weighing not less than one thousand 
pounds, when actually walking at the rate of two and one- 
half miles per hour during ten hours per day, ca,n exert a 
traction of one hundred poioids on a level road or a circular 
horse-path like that of the sweep powers. In order that a 
horse may exert his force most advantageously on a sweep- 
power the track should have a diameter of thirty to thirty- 
five feet, — never less than twenty-five. 

43. Increased Speed Diminishes the Traction 
Power. — If the horse walks more rapidly than two and 
five-tenths miles per hour, or at a slower pace, the force 
which he can exert changes also and is less or greater than 
one hundred pounds. Experience seems to indicate that 
at speeds between three-quarters of a mile and four miles 
per hour, and continued ten hours per day, the traction 
will be given by the following equation: 

2.5 miles x 100 r= n miles x Traction. 

Thus, at two miles per hour the traction w^ould be: 

2.5 X 100 =^ 2 X Traction; 
whence, Traction = ^f^^ or 125 lbs. 

What would be the traction at one mile per hour? at 
three miles? at four miles? 

44. Diminishing tlie Number of Hours of Worlt 
per Day Increases tlie Traction. — When the speed re- 
mains the same, experience has shown that, between five 
and ten hours per day, diminishing the time increases the 
possible traction in about the same ratio, or 

10 hours X 100 = n hours x Traction. 

Thus, if the horse is to be worked only five hours the 
traction he may exert will be 

10 X 100 = 5 X Traction, 
whence Traction = J V'" = 200 lbs. 

■'" What may the traction be when the horse works six 
hours? seven hours? eight hours? nine hours? 

45. Traction Power Diminished by Ip-Grades. — 

When a horse is forced to draw a load up a hill his power 
of traction is diminished by being forced to lift his own 
body at the same time. If he is going up a hill which 
rises one in ten he must expend a force of one hundred 



27 

pounds per one thousand pounds to overcome the force of 
gravity on his own body, and if the load he was drawing 
weighed one thousand pounds the force of gravity would 
require another one hundred pounds to overcome the tend- 
ency of the load down the hill, leaving all resistance out 
of consideration. Now if a loaded wagon weighs two 
tons, and the hauling of a ton on a level road of the same 
character as the hill requires one hundred and fifty pounds, 
then the force necessary to carry the load up the hill ris- 
ing one in ten would be, for a span of horses: 

For two horses 200 lbs. 

For load and wagon 400 " 

For rolling friction 300 " 

Total 900 " 

For one horse 450 " 

The rate at which the horses could move up the hill with 
this load would be, by 43, 

2.5 X 100= rate X 450; 
whence, rate=f f g=.55 miles per hour. 

What w^ould be the force required to move the same load 
up a hill which rises one foot in twelve feet? one foot in 
thirteen feet? one foot in fourteen feet? one foot in fifteen 
feet? 

46. Good Roads Make High Grades More Objection- 
able. — It is evident that the better the road-bed is made, 
thus reducing the traction on the level, the more objection- 
able a hill becomes, because the force of gravity is just as 
strong on a good road as on a bad one, and while a much 
larger load may be hauled on the level, when the hill is 
reached it cannot be drawn up. It was shown, in 45, that 
where the traction was one hundred and fifty pounds per 
ton, a grade of one foot in ten feet added to that traction 
one hundred pounds per one thousand pounds of load, in- 
cluding the weight of the team. Now if the road-bed were 
improved so as to reduce the traction to seventy-five 
pounds per ton, double the load could be brought to the 
hill, but unless the grade were also lessened, it could not 
be moved over it. 

47. Soft and Uneven Roads. — The reason why the 
traction is so heavy on soft and uneven roads will be read- 
ily seen from a study of Fig. 13. 



2a 



At A, where the wheel is continually cutting into the 
ground, it is, in effect, constantly tending to rise up a 
hill which is steadily breaking down, and whose gradient 
varies with the size of the wheel and the depth to which 
it sinks into the ground. A wheel four feet in diameter 
which sinks two inches into the ground is constantly 
tending to move up a hill which rises about one inch in 
five and one-third inches. If the wheel has a less diameter 
than four feet, not only does it sink more deeply into the 
ground with the same load, but, for the same depth, it is 
forced to tend to rise up a steeper grade. 




So, too, in raising the load over an obstruction, as 
shown at B, there is, in a measure, the effect of rolling the 
load up an inclined plane which is steeper in proportion as 
the height of the obstruction is large and the diameter of 
the wheel small. This case may, however, be more exactly 
compared to lifting a load with a bent lever of the first 
class, where the obstruction is the fulcrum, the distance 
a f the weight-arm and the distance 6,/ the power-arm. 
The higher the obstruction, and the smaller the wheel, the 
more nearly equal are the lever arms. It is this fact 
which explains, in part, why heavy loads may be moved 
more easily over uneven roads on large wheels. 

48. Wide and Narrow Wagon Tires — The same fact 
which makes a large wagon wheel more advantageous on 
soft ground makes a wide wagon tire better than a nar- 
row one, under the same conditions. It presents more 
surface to bear the load, and hence does not sink as deeply 
into the ground as the narrow one does, and, this being 
true, the load is moved with less traction. So far as 
lightness of draft is concerned, broad tires are best adapted 
to field hauling, but, for hard roads, there appears to be 
but little advantage in this particular. On soft roads the 



29 

broad tires would be of advantage, provided all wagons 
using the road were of this character, for then the cutting 
of the roads would be less and the draught lighter. There 
is, however, one serious disadvantage of wide tires on an 
improperly drained road composed of sticky soil : during 
wet times the w^heels so fill with mud between the spokes 
that the wagon becomes a load in itself. 

49. The Telford System of Road Construction.— 
The essential features of the system followed by this great 
English road-engineer may be briefly stated to consist in 
first leveling and thoroughly draining the road-bed, then 
to lay upon it a solid pavement of large stones, these cov- 
ered with a layer of stones carefully broken, and the whole 
then covered with a layer of gravel or other fine material. 
This was the system he followed in the highlands of Scot- 
land: 

But where much heavier traffic was to be provided for, 
the middle of the road-bed was made as firm as possible 
by forming a pavement of large stones which were care- 
fully laid by hand on a bed formed to the proper shape of 
the road and previously well drained. All inequalities 
were broken off the tops of these stones and the cavities 
filled in, the size of the stone being 7x3 inches. Over this 
paving was placed a layer of whinestone — a hard basaltic 

rock seven inches in thickness, the pieces being broken 

so that none should exceed six ounces in weight and all 
be able to pass through a circular opening two and one- 
half iiiches in diameter. This layer was again covered 
with biiiding gravel sufficient to fill up all the cavities. 
Great attention was paid to this road until it became 
thoroughly settled and then it stood the heavy traffic be- 
tween Carlisle and Glasgow for six years, nothing being 
required beyond cleaning the dirt off during that time. 

50. The Macadam System ot Road Construction.— 
This differed from the Telford system in that it aimed to 
secure, instead of the hard unyielding surface of that sys- 
tem, a certain amount of elasticity. Macadam, after pre- 
paring his road-bed essentially as described in the Telford 
system, laid upon it several inches of angular fragments 
broken from the hardest rock he could find, preference be- 
ing given to granite, greenstone or basalt. This layer was 
carefully watched by men. and as ruts appeared they were 



30 



raked full and fresh material added until a hard, even sur- 
face was secured. 

51. Road Drainage. — Perfect drainage is one of the 
first requisites of a good road, and in some places both 
surface and under drainage may be required. If the con- 
tour of a road is such that the water of rains may stand 
upon it in places, at all such points the road-bed softens 
and ruts are cut more or less deeply into it. In the con- 
struction of a road, therefore, the aim should be to give 
the surface such a contour that all rain is shed completely 
from it, and, at the same time, to depart as little from the 
horizontal section as possible. In Fig. 14 is given a pro- 
file of the Telford road-bed. 



'Road Bed. 



Surface 



CSyass 




Tif. /^ 

The section adopted by Telford is quite flat and more 
nearly a portion of the side of a fiat ellipse than the arc 
of a circle. It will be seen that in a road-bed thirty feet 
wide the fall, in the first four feet from the center, is only 
half an inch, in nine feet two inches, and in fifteen feet 
six inches. The aim is to have the road-bed as nearly flat 
as may be in the central eighteen feet so as not to tilt the 
load and force the traffic to follow one line. The tendency 
is to get the surface too sloping, and when this is done 
the weight of high loads is thrown more upon the lower 
set of wheels, which tends tj develop ruts on that side; 
there is also a tendency to slide, so that the wear on the 
road-bed and upon the wagon-tire is increased. The ridge, 
upon the two sides, is intended to keep stones and dirt 
from being thrown into the side drainage ditches. The 
road-bed is often made only eighteen feet wide and the two 
level strips used, one as a foot-path and the other as 
storage ground for crushed rock and gravel to be used in 
repairing the road. 

Where underdrainage is needed, two lines of tile are 
laid, one on each side just outside of the road-bed but in- 
side of the side ditches as shown in Fio-, 15. 



31 



The two lines of tile are used to j^revent water from 
running under the road-bed from either side to soften up 
the ground, the surface, when properly made and kept in 
repair, keeping water from entering from above. 



52. Results of General Morin's Experiments in 
France. — General Morin, after a series of experiments car- 
ried on at the expense of the French government, reached 
the following general conclusions regarding roads and car- 
riages: 

1. The traction is directly proportional to the load, and 
inversely proportional to the diameter of the wheel. 

2. Upon a paved or hard macadamized road the traction 
is independent of the width -of the tire wdien it exceeds 
three to four inches. 

3. At a walking pace the traction is the same for car 
riages with springs as for those without springs. 

4. Upon a macadamized or paved road the traction in- 
creases with the speed above a velocity of two and one- 
quarter miles per hour. 

5. Upon soft roads of earth or sand the traction is inde- 
pendent of the velocity. 

6. The destruction of the road is in all cases greater as 
the diameters of the wheels are less, and it is greater by the 
use of carriages without springs than of those with them. 

53. The Pulley. — This mechanical power consists of a 
wheel, having a grooved circumference through which a cord 
or chain may pass, and so mounted as to revolve freely 
about an axis. Pulleys are spoken of as either fixed or 
movable, according as the axis of revolution is stationary 
or travels with the load it carries. The two types are rep- 
resented in Figf. 1(). 

At A is represented a simple fixed pulley in whicli the 
power must be equal to the weight, because, in this case, 
the pulley may be regarded as a lever of the first class' 
where the axle of the pulley becomes the fulcrum, and then 



32 



the two arms are of equal length, each being a radius of 
the pulley. At B the lower pulley is movable, traveling 
upward with the load, and here we have the equivalent of 
a lever of the second class, with the fulcrum at the side of 
the pulley in contact with rope 2. As the load hangs 
from the axis of the pulley the power-arm is the diameter 
of the pulley and the weight-arm is the radius, giving us 
the equation: 

P. X P. A.=W. X W. A. 
or 5x2= 10x1. 



■^mm I 



© 



/If 



^©^^ 



@/'^ 



w 



® 



^)=/^ 




r,y./^ 



At C, D and E are combinations of several movable and 
fixed pulleys. In C we have a system with several sepa- 
rate cords, and in this the relation of power to weight is 
expressed by the equation 

P.x2^=W., 
where n equals the number of movable pulleys, or in C, 

P. X 2-'=W., 
whence, 4 x 2 x 2=r 16. 

In D and E we have two systems of pulleys where a 
sinfifle continuous cord is used. It makes no difference 
whether the pulleys are arranged side by side, as in D, or 
one above the other, as in E, the relation of power to 
weight is expressed by the equation: 

P. X No. cords supporting W. = W., 

whence for D, i x 1 — 16 

and for E, 1 x 6=:21. 

These equations always suppose no loss due to friction 
or in bending the ropes. There is, however, always a 
large and variable loss, so the actual lifting power is less 
than the theoretical. 



33 



54. The Horse-fork and Pulley. — The horse-fork and 
carrier are used in lifting hay, as represented in Fig. 17. 
The mechanical advantage is that of pulley B, Fig. 16, 
diminished, of course, by the friction. 

When no pulley is used next to the fork, the traction 
exerted by the horse must always considerably exceed the 
weight of hay lifted, so that a single horse is fully tasked 
in freeing from the load and raising from two hundred to 
three hundred pounds of hay. 







55. Using- the Pulley to Raise Heavy Stone Out of 
the (jround. — The pulley may frequently be used to ad- 
vantage in raising heavy stone out of the ground, and in 
pulling stumps, as shown in Fig. 18. 




If a pulley is lixed to the chain in either of the above 
cases, and the team draws upon a rope passing through it 
to a fixed attachment, as shown, two horses will exert the 
traction of four upon the stump or stone, diminished by 



the friction of the pulley. If the chain is attached to the 
stone, and so passed over the top as to roll, instead of 
drag, it from its place, the mechanical advantage will be 
still greater. 

56. The Screw. — This mechanical power is practically 
a combination of the inclined plane and the lever. The 
threads of the screw, and of the nut also, represent in- 
clined planes free to slide one upon the other. One or the 
other of these inclined planes is fixed while the other is 
moved by means of a lever of some form, the movable one 
carrvinji' the load. 

When the distance between the threads of a screw is 
one fourth of an inch and the circumference described by 
the end of the lever to which the power is applied is three 
feet, the theoretical load lifted by a power of one hundred 
pounds is 

100x3x^x12 = 14, too. 

But the friction is so variable, and so great with very 
heavy loads, that it is practically impossible to calculate, 
from theory, the load which may be thus moved. None of 
the mechanical powers can be so compactly constructed as 
this, and at the same time allow so small a force to exert 
so great a pressure. It is on this account that the screw 
is so much used in the construction of vices, liftincr-jacks 
and presses. 

57. Friction Between Solids. — When one surface 
rests upon another the roughness or inequalities of the 
one fit, to a greater or less extent, into those of the other, 
so that in order that one may be moved upon the other 
either the two bodies must be, to some extent, separated, 
or else the interlocking roughness must be broken away. 
We have seen that molecules are not in contact in bodies, 
and also that they are very small: from this it follows 
that no matter how smooth two surfacrs may appear there 
are always present inequalities of surface and always a 
resistance which opposes sliding, ' and this is called 
frk'tio/i. 

58. The Friction of Rest or Static Friction Be- 
tween Solids. — When two surfaces have been at rest with 
reference to each other for a time there is developed the 
maximum amount of interlocking, and hence the greatest 
amount of friction. This is analogous to a load standing 
upon a wagon over night, causing the wheels to become 



35 

depressed in the surface upon which they rest. The load 
is started with greater difficulty because the wheels must 
be rolled out of depressions, and this illustrates the condi- 
tion of static friction. On the other hand, if the wagon 
moves rapidly with its load, especially if over soft ground, 
the wheels do not have time to form deep depressions in 
the surface, and the resistance to forward progress is 
smaller, and this is, in a measure, analogous to friction of 
motion. 

59. The Friction of Motion or Kinetic Friction Be- 
^tween Solids. — When two surfaces are sliding rapidly 

one over the other there is not time to change direction 
and develop the interlocKing which is possible with a state 
of rest, and consequently less power is lost when one solid 
slides rapidly over another. 

60. Inflnence of Pressnre on tlie Friction of Solids. 
— When other things remain the same, increasing the pres- 
sure increases the friction, and the amount of friction is 
directly proportional to the pressure. Thus if one hun- 
dred pounds produce a friction of two pounds, one thous- 
and pounds will develop a friction of twenty pounds, and 
this is independent of the amount of surface bearing the 
load provided the pressure is not great enough to crush or 
tear the surfaces. 

61. Friction Between Liqnids and Solids.— In this 
case the amount of friction follows a different law, for it 
increases with the amount of surface and also with the 
square of the velocity of sliding motion. It is, however, 
less than that between solids and ' solids, and because of 
this fact the oiling of the bearings of machinery dimin- 
ishes very much the loss of effective energy through fric- 
tion. 

^ Where the velocities of revolution are slow, thick oils, 
like castor oil, develop but little friction, but as the speed 
is increased the friction increases very rapidly, and this 
fact makes a thick viscous oil inapplicable as 'a lubricant 
where high velocities, like those of the bowls of centri- 
fuges, are required. On the other hand, when a very thin 
fluid is used as a lubricant for slow motions there is time 
for such freely-flowing fluids to be crowded out of inequali- 
ties and thus allow the interlocking of solid surfaces to be 
partially set up and develop a high friction for these low 
speeds which the thick slow-flowing oils prevent; but for 



36 

very high speeds the thin fluid is able to maintain the de- 
pressions of the solid surfaces full, and the much smaller 
internal friction of the thin oil gives rise to a relatively 
lower friction for such speeds. 

It is upon this same principle, in part, that a thick 
grease serves so well the purpose of a lubricant to lessen 
friction in the slow sliding which obtains in the axles of a 
wagon. 

62. Bad Effects of Dirt in Journals.— When grit of 
any kind becomes entangled in the lubricants of any journal 
or friction surface these particles bridge across or cut the 
two films of oil which closely adhere to the two sliding 
surfaces, so that friction is set up between solids rather 
than between liquids as it should be, and there re- 
sults not only a great loss of energy transmitted by the ma- 
chine, but also an excessive wearing of the bearings, which 
quickly destroys the fit so essential to steady, easy and 
economical motion. Scrupulous cleanliness of the friction 
surface of farm machinery should therefore be adhered to 
as well as ample lubrication. 

63. Belting*. — The transmission of power by means of 
belting is a useful application of the friction between solid 
surfaces. In order that power may be economically 
transmitted by this means the belt must be so tight that 
little slipping takes place, and for leather belts this is 
least when the pulley is covered with leather, hair side out, 
and the belt runs upon this, hair side in. When the belt 
is running at a high speed the tension may be less in pro- 
portion to power transmitted, the activity of belting being 
expressed by the equation: 

Activity=Tv, 

where v is the velocity and T the effective tension. When 
the velocity is very great the tension may evidently be 
small, and yet the activity or horse -power remain large. It 
is on this account that small wire cables may be used at 
very high velocities in transmitting rery large amounts of 
energy. 

It is in consequence of this principle, too, that light 
rope are successfully used in transmitting energy to the 
centrifuge. 

64. Sliding Friction in Machinery is Lost Energy — 
The sliding of the inequalities of friction^surfaces over one 



37 

another sets the molecules constituting them into a to-and- 
fro motion, and all such motions represent energy lost either 
in the form of heat or of sound ; and it is because no ma- 
chine can be so constructed as to run absolutely friction- 
less that they, one and all, fail to transmit all the energy 
which is imparted to them, and hence it is that perpetual 
motion is an impossibility. 

65. Friction in the Chnrn. — In all forms of churns the 
agitation of the cream results in friction between the 
molecules of milk and between the milk and the parts of 
the churn, and this causes a transformation of the energy 
brought to the churn from the source of power largely into 
heat in the milk, which causes its temperature either to act- 
ually rise or else prevents it from cooling as rapidly as 
it would otherwise do. Now, if churning is begun with 
the cream at too high a temperature and the surrounding 
atmosphere is also too high, bad results must necessarily 
follow. 



STRENGTH OF MATERIALS- 



66. A Stress. — When a post is placed upon a founda- 
tion and a load of two thousand pounds set upon it, the 
post is undergoing or opposing a stress of two thousand 
pounds. When a rope is supporting a load of one thousand 
pounds in a condition of rest it is subject to a stress of 
one thousand pounds. The joists under a mow of hay are 
subjected to a stress measured by the tons of hay which they 
carry. 

67. Kinds of StresSi — Solid bodies may be subjected to 
three classes of stresses which tend to break them and will 
do so if the stress is great enough. These are : 

1. A crushing stress, where the load tends to crowd the 
molecules closer together, as when kernels of corn are 
crushed between the teeth of an animal. 

2. A stretching stress, as where a cord is broken by a 
load hung upon it. 

3. A twisting stress, as where a screw is broken by try- 
ing to force it into hard wood with a screw-driver. 

68. Strengtli of Moderately Seasoned White and 
Yellow PinePillars. — Mr. Chas. Shaler Smith has de- 
duced, from experiments conducted by himself, the follow- 
ing rule for strength of moderately seasoned white and 
yellow pine pillars: 

Rule. — Divide the square of the length in inches by the 
square of the least thickness in inches-, multiply the quotient 
by . 00 If- and to this jyroduct add 1 ; then divide <5, 000 by this 
su?n, and the residt is the strength in j^ounds X)er square inch of 
area of the end of the post. Multiply this result by the area 
of the end of the 2)ost in inches^ and the answer is the 
strength of the post in potmds. 

In applying this rule in the construction of farm buildings 
the timbers should not be trusted with more than one-sixth 
to one-fourth of the theoretical load they are computed to 
carry, because the theoretical results are based upon aver- 
ages, and there is a wide variation in the strength of in- 
dividual pieces. 



39 



Table of breaking load, in tons, of rectangular pillars 
of half seasoned white or yellow pine firmly fixed 

AND EQUALLY LOADED, COMPUTED FROM C. S. SmITH'S 
FORMULA. 





Dimensions of Rectangular Pine Pillars in Inches. 


♦J 


4x4 


4x6 


4x8 


4x10 


4x12 


6x6 


6x8 


6x10 6x12 


8x8 


8x10 


8x12 


10x10 


10x12 




tons. 


tons. 


tons. 


tons. 


tons. 


tons. 


tons. 


tons. tons. 


tons. 


tons. 


tons. 


tons 


tons. 


a 


12.1 


18.1 


24.2, 30 2 


36 3 


44.5 


.59 . 3 


74 1 


88.9 


101.7 


126 9 


1.52.3 


182.7 


219.2 


10 


8.7 


13.0 


17.4' 


21.7 


26.1 


34 6 


46.2 


0( .1 


69.2 


84 2 


105.3 


126.3 


1.58 6 


190 3 


12 


6.5 


9.7 


12.9 


16.1 


19.4 


27.2 


36.3 


45.4 


.54.4 


69.7 


87.1 


104 5 


136 7 


164.0 


14 


5.0 


7.4 


9.9 


12.4 


14 9 


21.7 


29.0 


36.2 


43.5 


57.9 


72.3 


86,8 


117 4 


140.9 


16 


3.9 


5.9 


7.8 


9.8 


11.7 


17.7 


23.5 


29 4 


35,3 


48 4 


60.6 


72 7 


101 


121.2 


18 












14.6 


19.4 


24.3 


29.1 


40.8 


51.0 


61 2 


87.2 


102.6 


20 












12 2 

10.3 
8.8 


16.2 
13.7 
11.7 


20.3 
17 2 
14.7 


24.3 

20 6 
17.6 


34.8 
29 . 9 
25.9 


43.4 
37.4 
32.3 


52 1 

44.8 

38 8 


75.7 
65.8 
57.9 


90 8 


22 












79 


24 








69 4 

















69. Tensile or Stretching Strength of Timber.— 

The tensile strength of materials is measured by the least 
weight which will break a vertical rod one inch square 
firmly and squarely fixed at its upper end, the load hang- 
ing from the lower end. Below are given the results of 
experiments with different varieties of wood, but the 
strengths vary greatly with the age of the trees, with the 
part of the tree from which the piece comes, the degree of 
seasoning, etc. 

Elm 6,000 lbs. per. sq. in. 

Am. Hickory _ 1 1,000 " '' '^ '• 

Maple 10,000 " " " " 

Oak, white and red 10,000 " '• " " 

Poplar 7.< 00 " " " " 

White pine 10,000 " " " " 

70. Tensile or Cohesive Strength of Other Materi- 
als. — 

Am. cast iron 16,000 to 28 000 lbs. per sq. in. 

Wrought iron wire, annealed. .... 30,000 to 60,000 " '• " " 

Wrought iron wire, hard 50,000 to 100,000 " " " " 

Wrought iron wire ropes, per sq. in. of rope 38,0ii0 " " " " 

Leather belts, 1,500 to 5,000, good 3,000 " '• •' " 

Rope, manilla, best 12,000 '' " " " 

Rope, hemp, best 15,000 " " " " 

71 Transverse Strength of Materials. — When a 

board is placed upon edge and fixed at one end as repre- 



40 



sented at A, Fig. 19, a load acting at W puts the upper 
edge under a stretching stress. 




We know from experience that in case the board breaks 
under its load when so situated the fracture will occur 
somewhere near 5-6. Now in order that this may take 
place, there must be, with white pine, according to 69, 
a tensile stress at the upper edge of ten thousand pounds 
to the square inch, and if the board is one inch thick the 
upper inch should resist a stress of ten thousand pounds at 
any point from 5 to 1 ; but we know that no such load will 
be carried at W. The reason for this, and also for its 
breaking at 5 rather than at any other point, is found in 
the fact that the load acts ujoon a lever arm whose length 
is the distance from the point of attachment of the load to 
the breaking point, wherever that may be, and this being 
true the greatest stress comes necessarily at 5. 

If the board in question is 48 inches long and 6 inches 
wide, it will, in breaking, tend to revolve about the cen- 
ter of the line 5-6, and the upper three inches will be put 
under the longitudinal strain, but according to 69, is ca- 
pable of withstanding 

3 X 10,000 lbs. = 30,000 lbs. 

without breaking; but in carrying the load at the end, as 
shown, this cohesive power is acting at the short end of a 
bent lever whose mean length of power-arm is one-half of 
4-5 or 1.5 inches, while the weight arm is forty-eight 
inches in length. It should, therefore, only be able to hold 
at W. 937.5 pounds; for 

asP. xP. A. = W. X W. A., 

we have, 3,000 x 1.5 = W. x 48, 

whence W. = ili^« = 937,5 lbs. 

48 

When a board, in every respect like the one in A, Fig. 
19, is placed under the conditions represented in either B 



41 



or C, Fig. 19, it should require just four times the load to 
break it, because the board is practically converted into 
two levers whose j^ower-arms remain the same, but whose 
weight-arms are only one-half as long each. 

72. The Transverse Strength of Timbers Propor- 
tional to the Sqnares of their Vertical Thicknesses. — 
Common experience demonstrates that a joist resting on 
edge is able to carry a much greater load than when ly- 
ing flatwise. If we place a 2 x 4 and a 2 x 8, which differ 
only in thickness, on edge, their relative strengths are to 
each other as the squares of 4 and 8, or as 16 to 64. That 
is, the 2x8, containing only twice the amount of lumber 
as the 2 x 4, will, under the conditions named, sustain four 
times the load. The reason for this is as follows: In Fig. 
20 let A represent a 2 x 4 and B a 2 x 8. 




w tn. 



14/ 





Ti^'JO 



In each of these cases the load draws lengthwise upon 
the upper half of the joist, acting through a weight-arm 
F. W. ten inches in length, to overcome the force of co- 
hesion at the fixed ends, whose strength, according to 69^ 
is ten thousand pounds per square inch, or a total 

of 2 X 2 X 10,000 lbs.=40,000 lbs. in the 2 x 4 joist, 
and of 2 X 4 x 10,000 lbs.=80,000 lbs. in the 2x8 joist. 

These two total strengths become powers acting through 
their respective power-arms F. P., whose mean lengths 
are, in the 2x4 joist, one inch, and in the 2x8 joists, two 
inches. 

Now we have, from 29, 

P. x P. A.=W. X W. A., 



42 

and substituting the numerica] values, in the 2 x -t joist, we 
get 

4xl0,000xl = W.xl0, 
or 4 X 10,000=10 W., 
and W =1,000. 

Similarly, by substituting numerical values in the case of 
the 2x8 joist, we get 

8 X 10,000 X 2=W. X 10, 

or 16x10,000=10 W., 

and W.=16,O0O. 

It thus appears that the loads the two joists will carrj'- 
are to each other as four thousand is to sixteen thousand, 
or as one is to four; but squaring the vertical thickness of 
the two joists in question we get for the 2x4 joist 

4 X 4=16, 

and for the 2x8 joist 

8 X 8=64; 

but sixteen is to sixty-four as one is to four, which shows 
that the transverse strengths of similar timbers are i^ropor- 
tional to the squares of their vertical diameters, 

73. The Transverse Strength of Materials Dimin- 
ishes Directly as the Length Increases. —It will be 
readily seen from an. inspection of Fig. 20, that lengthen- 
ing the pieces of joists, while the other dimensions re- 
main the same, lengthens the long arm of the lever, while 
the short arm remains unchanged; and since the force of 
cohesion remains unaltered, the load necessary to overcome 
it must be less in proportion as the lever arm upon which 
it acts is increased. Thus, if the 2 x 8 in Fig. 20 is made 
twenty inches long, we shall have, from 29- 

P.xP. A.=W.xW. A. 

and by substituting the numerical values we get 

80,000x2=W.x20. • 

hence 

W.=8,000, 

instead of sixteen thousand, as found in 72- 

74. The Constants of the Transverse Breaking 
Strength of Wood. — Since the laws given in 71^ 72 and 
73 apply to all kinds of materials, it follows that the act- 



4-] 

ual breaking strength of different kinds of materials will de- 
pend upon the cohesive power of the molecules as well as 
upon the form and dimensions of the body which they 
constitute. The breaking strength of a beam of any mate- 
rial is always in proportion to its breadth, multiplied by 
the square of its depth, divided by its length, or, 

Breadth x the square of the depth 
its length^ ~ 

and if the breadth of a piece of white pine in inches is four, 
its depth in inches ten, and its length in feet ten, we shall 
have, taking the length in feet, 

4x10x10 _ 
— 1,— =40. 

Now if we find by actual trial, by gradually adding weights 
to the center of such a beam, that it breaks at eighteen 
thousand pounds (including half its own weight), the ra- 
tio between this and forty will be 

18,000 ,_ 

and as this ratio is always found for white pine, when the 
breadth and depth are taken in inches and the length in 
feet, no matter what the dimensions of the timbers may 
be, four hundred and fifty is called its breaking co?istant fo)- 
a center loud. 

For other materials this constant is different, and has 
been detei'mined by experiment and given in tables in va- 
rious works relating to such subjects. The following are 
taken from Trautwine: 

75. Breaking: Constants of Transverse Streni^th of 
Dill'erent Materials. — 

WOODS. 

American White Ash 650 lbs. 

Black Ash (300 " 

Yellow American Birch SoO " 

American Hickory and Bitter-nut 800 " 

Larch and Tamarack 400 " 

Soft Maple ' * ' ' . ' 750 " 

American White Pine 1:50 " 

American Yellow Pine 500 " 

Poplar ..!!... 550 " 

American White Oak 600 " 

American Red Oak 800? " 



44 



METALS. 



Cast iron 1,500 to 2,700 lbs. 

Wrought iron bends at 1,900 to 2,600 lbs. 

Brass 850 lbs. 



70, To flml the Quiescent Center Breaking Load of 
Materials liaring* Kectangular Cross-sections when 
Placed Horizontally and Supported at Both Ends. — 

In placing joists and beams in barns it is important to 
know tlie breaking load of the timbers used. This may be 
determined with the aid of the following rule and the table 
of constants given in 75: 

RcTLE. — 3Iultiplij the square of the depth in inches by the 
breadth in inches and this by the breaking constant given in 
75; divide the result by the clear length in feet, and the re- 
sult is the load in pounds. 

But in the case of long, -heavy timbers and iron beams 
one-half of the clear weight of the beam must be deducted 
because they must always carry their own weight. 

Square of ] 

depth [- X Breadth in inches x Constant 
in inches ) 

Brea' ing load=-^ • 

Length in feet. 

What is the center breaking load of a white pine 2 x 12 

joist twelve feet long? 

T. 1- , ^ 12x12x2x450 -.^onmu 
Breaking load= -^ =10,800 lbs. 

What is the breaking load for the same ten feet long? 
fourteen feet long? sixteen feet long? eighteen feet long? 

Solve the same problems for other woods. 

77. Greneral Statements Regarding the Quiescent 
Breaking Loads of I niform Horizontal Beams . — If 
the center quiescent breaking load be taken as 1, then, 
when all dimensions are the same, to find the breaking 
load : 

(1) When the beam is fixed at both 6nds and evenly 
loaded throughout its whole length, multiply the result 
found by 76 by two. 

(2) When fixed at only one end and loaded at the other, 
divide the result obtained by 76 by four. 

(3) When fixed only at one end and the load evenly dis- 
tributed, divide the result obtained by 76 by two. 

(4) To find the breaking load of a cylindrical beam, first 



45 



find the breaking load of a square beam having a thickness 
equal to the diameter of the log and multiply this result 
by the decimal .589. 

78. Breaking- Load of Rafters.— In finding the 
breaking load of timbers j^laced in any 'oblique position as 
show in Fig. 21, take the length of the rafter equal to the 
horizontal span AC and proceed as in 76 and 77 

79. Table of Safe Quiescent Center Loads for Hor- 
izontal Beams of White Pine Supported at Both 
Ends. — In this table the safe load is taken at one-sixth 
of the theoretical breaking load. This large reduction is 
made necessary on account of the cross-grain of timbers 
and joists and the large knots which weaken very materi- 
ally the pieces. Where a judicious selection is made in 

placing the joists, lay- 
ing the inherently weak 
pieces in places where 
little strain can come 
upon them, much sav- 
ing of lumber may be 
made. 




03 

a 

o 


Span 10 feet. 


! 

Span 12 feet. 


Span 11 feet. 


Span 16 feet. 


K 


Breadth. 


Breadth. 


Breadth. 


Breadth. 


Eh 

a, 

Q 


2 in 


4 in. 


6 in. 


2 in. 


4 in. 


6 in, 


2 in. 4 in. 

1 


6 in. 


2 in. 


4 in. 


6 in. 


4 

6 

8 

10 

12 


Z6.S. 
240 

540 

960 

1500 

2160 


lb.<t 

480 

1080 

1920 

, 3000 

4320 


Ib.f. 
720 
1620 

2880 
4500 
6480 


lbs. 

200 

450 

800 

12.50 

1800 


lbs. 

400 

900 

160) 

2500 

3600 


lbs. 
600 
13-0 
2400 
37-^0 
5400 1 
1 


lbs. 
172 

386 

686 

1072 

1544 


lbs. 

772 
1372 
2144 

3088 


lbs. 
516 
1158 
2058 
3216 
46.32 
1 


lbs. 
1.50 
336 
600 
936 
1350 


lbs. 
3uu 
672 
1200 

1872 
2700 


lbs. 
450 
1008 
1800 
2808 
4050 




Breadth. 


Breadth. 


Breadth. 


Breadth. 




8 In. 


10 in 


I'i in 

lbs. 
1440 
3240 
57(50 
9000 
12960 


8 in. 


10 in 13 in 

! 


8 in. 


10 in' 


13 in 


8 in. 

Z6.?. 
600 
1344 
2400 
3744 
54lX>: 
I 


10 in 


13 in 


4 

6 

8 

10 

12 


lbs 
960 

2' 60 
38401 
6000| 
8640 


lbs. 
1200 
2700 
4800 
7500 
10800 


lbs. 
800 
1800 
3200 
5000; 
7200 


lbs. 
1(X)0 
2250 
4000 
6250 
9000 


lbs. 
1200 
2700 
4800 
7500 
10800 


lbs. 

688 
1544 
2744 
4288 
6176 


lb.9. 
860 
1930 
3430 
5360 
7720 


lbs 

1032 

2316 

4116 

6432 

9264 


lbs. 
750 
1680 
3000 
4680 
6750 


lbs. 
900 
2016 
3600 
5616 
8100 



• 
• 


m 
• 


• 
• 


• • • 






9 
• 


• 
• 


# 
• 

• 


• • • 
9 9 m 

9 9 9 







FLUIDS. 



80. Surface Tension of Liquids. — The molecules of 
liquids exert an attractive force ujjou one another, but this 
is most manifest at their surfaces because the interior 
molecules, being pulled equally on all sides by surround- 
ing molecules, have their tendency to move balanced in 
every direction. The surface conditions, however, are dif- 
ferent, as will be seen from Fig. 
22, where the arrows at A and 
B show the direction of the ac- 
tion of molecular forces on the 
interior and surface molecules 
respectively. The unbalanced 
condition of forces between the 
surface molecules of liquids 

causes them to act like a thin ^'i^- ^''• 

elastic membrane or skin upon the liquid within. It is the 
tension of these films which causes rain drops, and the shot 
from the shot towers to assume the spherical form when 
falling. The same action gives this form to the fat glob- 
ules of milk, to dew drops on cabbage leaves and to drops 
of water on a dusty surface. It is the same surface ten- 
sion which sustains a fine needle on the surface of water 
and which enables certain insects to walk upon water. 

81. Streni;tli of Surfiu-e Tension.— The strength of 
the tension of fluid surfaces is difl'erent for ditferent liquids, 
and it varies with the surfaces which are in contact. The 
following: table o-ives the relative surface tensions in cer- 
tain cases : 

Between clear water and air 82, nearly. 

Between olive oil and air .' 37, nearly. 

Between chloroform and air 31, nearly. 

Between water and olive oil 21, nearly. 

Between water and chloroform 30, nearly. 

These ditferences of tension give rise to a great variety 
of phenomena. When oil is placed on water it tends to 
spread out indefinitely in a thin sheet. On the other 
hand, if a little water is placed upon chloroform it tends 



to draw it into a sphere or drop. The reason for these facts 
will be understood from Fio\ 28. 



?^3r£ii£4^ 



Fi(/. 23. 

In A, on the circumference, where the drop of oil, air 
and water meet the surface molecules are actuated by three 
sets of forces represented in direction by the arrows and 
in intensity by the numbers, and it is evident that the 
molecules so affected must move in the direction of the 
stronger force, and as the surface tension of the water-air 
surface is strongest, the oil is drawn out indefinitely until 
an extremely thin film results. It is on this account that 
so small a quantity of oil put overboard by a vessel at 
sea, in times of storm, covers so large an area as often to 
effectually protect the vessel from the dangers of wave- 
action. It is in accordance with the same principle that 
water and other fluids spread out over the surfaces of solids 
which they will wet. 

in the case of B, where a drop of water is j)laced upon 
chloroform, the conditions of A are reversed and the water 
at first tends to draw up into a sphere. It is in the same 
manner also that water on a dusty floor or on cabbage 
leaves is draw^i up into drops, 

82. Capillary Action. — When slender glass and other 
tubes, whose adhesive force for water is greater than the 
attraction of the molecules of water for one another, are 
placed vertically in water, the water is seen to rise in 
them and come to rest above the level of the water in the 
surrounding vessel. It will also be observed that the height 
attained by the water in dilferent tubes varies inversely 
as their inside diameters. The rise of liquids in slender 
tubes is in accordance with the principle illustrated in Fig. 
23 A, the chief ditference being that the movement is in 
opposition to the force of gravitation and that the rise is 
checked when the down pulling forces balance the surface 
tension. 

The rise of water in soil and of oil in a lamp wick are 
other instances apparently due to a closely allied, if not 
identical action. 



48 ■ 

If oil the other hand, the attraction between the liquid 
and the walls of the tube is less than the attraction among 
the molecules themselves, so that the walls are not wet by 
it, the surface of the liquid in the tube is depressed, the 
amount beino- p-reater as the diameter of the tube is less. 
This depression is in accordance with the principle ex- 
plained under B, Fig-. 2o. 

83. Iiilliieiice of Surface Tension on Lactometer 
Reading's. — The rise of water on the sides of a tube tloat- 
iny- in it, as in the case of the lactometer, tends to draw it 
more deeply into the liquid and thus gives it a higher read- 
ing. On the other hand, if the liquid has its surface tension 
weakened by being overspread with oil, or if the stem of 
the lactometer is made greasy by handling or otherwise, 
it will then be lifted out of the liquid and too low a read- 
ing vvill be indicated. It is important, therefore, in de- 
termining the specific gravity of milk by this method to 
see that the lactometer is thoroughly clean. 

84. Solution of Solids in Liquids. — When salt is 
placed in water the adhesion between the molecules of 
water and salt is at tirst stronger than the cohesion 
between the molecules of salt, and successive layers of salt 
molecules are separated and disseminated through the 
liquid. If the quantity of salt placed in the water be 
large enough, there will come a stage when the quantity 
of salt dissolved in the water has so weakened its adhesive 
power that it ceases to be strong enough to overcome the 
molecular cohesion of the salt and at this stage further 
solution is stopped. 

In the majority of cases w^here solids are being dissolved 
a rise of temperature so weakens the cohesive force that 
solution may be carried still further. It is in part the 
greater solubility of soil ingredients in water at high tem- 
peratures than at low that makes a ^varm soil more con- 
ducive of plant growth than a cold one. 

85. Diffusion. — When a phial, nearly full of salt or 
sugar, is placed in a vessel and the vessel carefully tilled 
with water so as to cover the phial, the salt or sugar will 
in time be dispersed through the whole water. The rate 
at which this (/tjf'usio/i takes place is different for different 
substances, and in the table below, the numbers indicate 
the relative lengths of time required for different substances 
to travel the same distance in water under like conditions. 



49 

Hydrochloric acid 1 

Salt 3.33 

Sugar 7 

Maguesium sulphate : 7 

Albunieu 49 

AH substances diffuse more rapidly at moderate temper- 
atures then at low ones, and here is another reason why 
a warm soil is more conducive to plant growth than a cold 
one, for the transfer of food from soil to plant is partly a 
process of (^iffuttio/t. 

If two gases are placed in two vessels and an opening 
be made connecting them, the molecules of each kind of 
gas will travel from their respective vessels and enter the 
other until a uniform mixture results. We have seen that 
the velocities with which molecules travel are inversely 
porportional to their densities, and it is found that the 
rate of diffusion of gases obeys the same law, the lighter 
gas diffusing more rapidly. 

Oxygen enters the air cells of our lungs and carbon 
dioxide leaves them by this process of diffusion, and the 
same thing is true of the intercellular air passages of 
leaves into which the stomata lead. 

80. Osmosis,— In case two liquids, which mix, are 
placed on opposite sides of a porous membrane capable of 
being wet by one or both of them, currents are estab- 
lished in one or both directions. The membrane first be- 
comes pentrated by the liquid having the strongest attrac- 
tion for it, and on reaching the other side the liquid ditt'us- 
ing into it causes its attraction for the walls to be les- 
sened, and this allows this portion to be crowded out into 
the liquid which has been approached and a stream thus 
established. If the pores in the membrane have a diame- 
ter exceeding ^su^sxi inch, a return current of the second 
liquid is established toward the first along the central por- 
tion of the pores. It is by this process that the tissues of 
plants and animals are nourished. Here again a warm 
temperature makes the streams more rapid, and so still 
another reason is found for havino; the soil in which the 
roots grow sufficiently warm. 

Osmose of gases as well as of liquids also takes place, 
and it is by this process that animals get their supply of 
oxygen and plants their supply of carbon dioxide. 

87. Viscosity. — When the molecules constituting any 
body are forced to move past one another their mutual mo 



50 

lecular attraction causes a dragging which sets the dis- 
turbed molecules vibrating, and this moUcular vibration 
is at the expense of the energy which produced the move- 
ment. This dragging effect of the molecules is called vis- 
cosity^ and the amount of energy transformed into heat in 
consequence of it is a measure of the viscosity. The fat 
globules in rising through milk serum encounter this vis- 
cosity, and a part of the energy of the creaming force is 
transformed into heat, causing the cream to rise more 
slowly than it would if there were no viscosity. 

Liquids, in flowing through pipes or other channels, are 
retarded by viscosity so much that in long and slender 
pipes the amount of water discharged is very much dimin- 
ished. This fact makes it necessary, in tile draining and 
in conveying water in pipes to pastures or other points, 
to use larger pipes than would Otherwise be necessary. In 
all those cases where the liquid wets the surface past which 
it flows the friction is due wholly to the viscosity of the 
fluid, for the layer in immediate contact with the sur- 
face remains stationary while the other molecules move past 
them. This is the case with oils used to diminish friction 
in machinery. 

When the inner surfaces of pipes are rough and uneven 
the flow of liquids through them is further diminished by 
the direction of the current being changed at these in- 
equalities and thrown toward the center of the pipes 
across the course of the central current. It is important, 
therefore, in selecting tile to avoid those having rough in- 
teriors, and also in laying them to avoid making shoulders 
at the junctions of the many sections. 

The viscosity of air and other gases is due to the pro- 
miscuous traveling of the molecules, which causes those mov- 
ing transverse to the stream to be caught in it and thus re- 
tard the onward movement, acting much as the eddy-cur- 
rents set up by inequalities in the surface of water pipes. 

88. Pressure of Fluids. — The great freedom of motion 
of molecules in masses of liquids and gases causes them to 
exert an internal and to transmit an external pressure equal 
and undiminished in all directions. The proof of this law 
for liquids, is found in the fact that when two vessels are so 
connected that water can flow from one to the other the 
water will have the same height in both vessels, no mat- 
ter what form or direction the communicating passage may 



51 



take. The spherical form of a soaj) bubble in mid-air 
proves the law true for air; for if the pressure from all 
sides were not equal the form of the bubble would change 
from that of a sphere. 

89. Pressure of Liquids iu Yessels.— The pressure 
exerted by liquids on the walls of vessels which contain 
them is due to their weight, and, for a given liquid, is 
always proportional to the depth. In the following table 
the weight of water per cubic foot and pressure per square 
foot are given for different temperatures: 







Pressure in lbs. per sq 


>. FT. AT DIFFERENT DEPTHS. 


Tern. 


Lbs. per 
cu. tt. 














Fahr. 


















At 2 ft. 


At 4, ft. 


At 8 ft . 


At 10 ft. 


At 30 ft . 


At 40 ft. 


32« 


62.417 


124.83 


249 67 


499 34 


624.17 


1248.34 


2476.68 


39°. 2 


62.425 


124.85 


249.70 


499.40 


624 25 


1248.50 


2497.00 


40° 


62.423 


124.85 


249.69 


499.38 


624.23 


1248.46 


2496 92 


50° 


62 409 


124.82 


249.64 


499.27 


624.09 


1248.18 


2496 36 


60° 


6^.367 


124.73 


249.47 


498.94 


623.67 


1247.34 


2494.68 


70° 


62.302 


124.60 


249.21 


498 42 


623 02 


1246.04 


2492.08 


80° 


62.218 


124.44 


248.87 


497 74 


622.18 


1244.36 


2488.72 


90° 


62.119 


124.24 


248.48 


496 95 


621.19 


1242.38 


2484.76 


212° 


59.7 


119.40 


238.80 


477.60 


597.00 


1194 00 


2388.00 



The pressure of the water on the bottom of a vessel can 
always be found by multiplying the area of the bottom in 
square feet by the depth of the water, and this product by 
the weight of a cubic foot of water, which is nearly Q2A2. 

P. on bottom=area x depth x 62.42. 

The lateral or side pressure is proportional to the depth, 
following exactly the same law as that for the 
pressure on the bottom. Since the depth at the surface is 
zero, the lateral pressure is also zero, and since the depth 
at the bottom of a vessel is the greatest, the lateral pres- 
sure must there be at its maximum; these being true, the 
mean pressure on the side of a vessel would be the pressure 
at one-half the depth of the liquid, and, hence to find the 
total pressure on the side of a vessel, we have 



Total lateral P. 



Area of sides x depth x 62.42. 



What is the total pressure on the bottom and on the 
sides of a reservoir 6x6x6 feet filled with water at 
39.2° F. ? at 80° F. ? 



52 



What is the lateral pressure on the lower six inches of a 
cylindrical tank ten feet in diameter filled with water to a 
depth of ten feet? 

If this.pressure is to be sustained by an iron hoop composed 
of one-eighth inch band iron, how wide should the hoop be? 

90. Pressure of Grraill ill Bins. — The downward pres- 
sure of grain in bins follows the same law as that of liquids, 
but the lateral pressure is always less on account of the 
friction between the kernels. When grain is heaped up on 
a level surface it is found impossible to pile beyond a cer- 
tain height without increasing the diameter of the pile at 
the base. A certain angle of slope is maintained, which 
for wheat is about 31°, about 30° for shelled corn, and for 
oats about 34*^. 

The friction of the kernels upon* one another is just great 
enough to maintain this angle, but in filling a bin with 
wheat, for example, introducing it at the center, after a 
certain quantity has been added the base of the cone is 
extended until it reaches the sides of the bin, and the ad- 
dition of any further quantity brings into existence an 
outward pressure on the walls of the bin tending to spread 
them. The case is analogous to the retaining icalls which 
are often built to prevent sand or earth from caving or 
sliding. The amount of this pressure and the method of 
computing it will be understood from Fig. 24. 

CMMC represents a section of a bin sixteen feet square 
and eight feet deep filled with shelled corn. The cone 
MOM represents the cone 
of grain which exerts 
no pressure on the sides 
of the bin. The remain- 
ing portion MOMCC has 
its weight divided be- 
tween the sides and the 
bottom, the sides pre- 
venting it from sliding 
down the inclines OM, 
OM. The pressure on the 
theory of retaining 




Fig. 24. 



side CM, according to the 
walls, is equal to the weight of 
tCM, "acting as a wedge between the surfaces tM and CM. 
As the wedge is a movable inclined plane where the force 
acts parallel to the base, the pressure may be computed 
from the equation 



53 

Power X base=weight x height. 

The height, tC, is 4.5 feet, and the base CM, eight feet. 
The weight is the weight of corn composing the wedge, 
and is equal to 

4.5 X 8 X 16 X 1728 x 56 
23r2l50:4 =12958.72 lbs. 

Substituting the numerical values in the equation of the 
wedge above we get 

Power X 8 = 12958.72 x 4.5, whence, power^=7289.28 lbs. 

as the total pressure on the side of the bin, which is an 
average of 50.9 pounds per square foot, 

91. The Principle of Flotation. — When a body is im- 
mersed in a fluid it is pressed or lifted upward with a force 
exactly equal to the weight of the fluid it displaces, and it 
is because of this fact that stones can be moved so much 
more readily under water than out of it. Thus, a stone 
containing exactly one cubic foot will be lifted up, when 
in water, with a force of 62.42 pounds, and hence appears 
that much lighter when moved under those conditions. It 
is this principle which makes possible water navigation 
and the ascension above the earth"s surface in balloons. 

92. Specific Gravity. — When the specific gravity of 
cast iron is spoken of as 7.2 the meaning is that a cubic 
inch or a cubic foot of that body weighs just 7.2 times as 
much as the same volume of water, and when the specific 
gravity of white pine is given as .4 the meaning is that a 
given volume of that wood weighs only .4 as much as an 
equal volume of water; hence, for liquids and solids, we 
have the equation 

. . . wei ght of body 

p c gravi y ^g^gj^i; q^ equal volume of water. 

Air is taken as the standard of specific gravity for gases. 

93. To Find the Specific Gravity of Solids.— The 

principle of flotation affords a very simple means of find- 
ing the specific gravity of solids. Since any body immersed 
in water displaces its volume of water, and since it is also 
buoyed up by a weight equal to that of the water displaced, 
it is only necessary to weigh the body whose specific grav- 
ity is desired, both in air and in water, the difference in 
weight giving always the weight of a volume of water the 
size of the body whose specific gravity is sought. The 



54 - 

weight of the body in air divided by this difference gives 
the specific gravity, and hence the rule 

weight of solid in air 
Specific gravity=jQgg ^^ ^^-^^^^ ^^ ^^^.^^ 

Suppose a body weighs ten in air and when immersed in 
water only eight. In this case the weight of a volume of 
water equal in size to that of the body is 

10-8=2 
and hence, by the rule above, we have 

Specific gravity = —=5. 

Find the specific gravity of a body weighing fifteen in 
air and fourteen in water. What will be its specific grav- 
ity if it weighs in water; three? one? four? six? seven? 
ten? twelve? 

94. Table of Specific Gravities and Weights per 
Cubic Foot of Dilfereut Substances.— 

Sp. gr. Weight. 

Ash, Am. white, dry 61 38 lbs. 

Anthracite coal, moderately shaken 58 " 

Brick, common hard 125 

Carbon dioxide, referred to air 1.5 " 

Charcoal, pines and oaks 22 

Clay, dry, in lump, loose _ 63 

Coal, bituminous 1 . 35 81 

Coal, bituminous, broken, loose 50 

Copper, rolled ... 8.9 555 

Earth, clay loam, dry. nat. condition 70 || 

Earth, clay loam, saturated 93 

Earth, reddish clay, dry, nat. condition 88 ''^ 

Earth, reddish clay, saturated 108 

Earth, fine sand, nat. condition 106 " 

Earth, fine sand, saturated 121 

Elm, dry 56 35 '^' 

Gypsum, ground, loose 56 

Gravel 106 || 

Hemlock, dry s 4 '^^ 

Hickory, dry 85 53 " 

Iron,cast 7.21 450 

Ice.. 92 57.4 " 

Lard 95 59.3 " 

Lead 11-38 709.6 || 

Limestone, broken 1-5 96 

Maple, dry 79 49 " 

Oak, white, dry 77 48 || 

Oak, red, black, dry 39 



55 



Spgr. 
.40 
.55 



Weight. 
25 lbs. 



.85 



34.3 " 

45 " 

151 " 

8.5 " 

15.50 " 
490 " 

62.35 " 



Pine, white, dry 

Pine, yellow, northern 

Salt, coarse 

Sand stone 2.41 

Snow, fresh fallen 

Snow, compacted by rain 

Steel 7 , 

Water, 62° P 1 

95. To Find the Specific Gravity of Liquids. — The 

principle of flotation stated in 91 also furnishes an easy 
method of finding the specific gravity of liquids, which is 
done as follows: Find the difference in weight of any con- 
venient solid in air and in water and then in the liquid 
whose specific gravity is desired. Suppose the solid se- 
lected loses a weight of one in water and a weight of .75 
in another liquid, then a volume of water, the size of the 
body taken, weighs one, and an equal volume of the second 
liquid weighs .75. Then by the rule we have: 



to 



Sp. gr. =—^ =.75 

96. The Lactometer. — The use of the lactometer in 
determining the specific gravity of milk is also an appli- 
cation of the principle of flotation, and is simply a modi- 
fication of the method in 95. In this instrument, as shown 
in Fig. 25, the slender and uniform stem is graduated so 
as to give the specific gravity by direct reading. 

97. Atmospheric Pressure. —The air which every- 
where envelops the earth to a depth prob- 
ably exceeding five hundred miles has 
weight and exerts a pressure m all di- 
rections upon all bodies in it. This 
pressure at the level of the sea, is capa- 
ble of sustaining a column of mercury 
29.922 inches high on the average when 
the temperature is at .32° F. and is 
equal to a pressure of 14.73 pounds to 
the square inch. The amount of this 
pressure depends always upon the total 
quantity of air that exists at the time 
above the point where the pressure is 

^^' ""^ exerted. This being true, places situ- 

ated above the level of the sea have a less pressure because 
they are nearer the upper limits of the air. 



I 



5G . 

98. Yariatioiis in Atmospheric Pressure. — The pi es- 

sure exerted by the air at any place is almost constantly 
changing, so that it is rarely the same at any two con- 
secutive moments: these changes are not as a rule very 
large or very rapid. A change of one-half a pound to the 
square inch in twenty-four hours is a large change, and a 
change of one pound to the square inch never occurs during 
short intervals, except when very violent storms are in 
progress. These changes in pressure are due to the fact 
that the air is disturbed by currents and waves which owe 
their origin to various causes. 

99. Soil Breathing*. — When the atmospheric pressure 
is heavy over a given locality the air is driven into the 
air passages in the soil of that place, and then when the 
pressure changes again, becoming lighter, the compressed 
air expands and escapes ; thus there is maintained an ir- 
regular but constant breathing of the soil in consequence 
of these changes in atmxospheric pressure. The soil breath- 
ing is further maintained, especially during the growing 
season, by the daily changes in temperature which occur 
in the upper thirty inches of soil. During the day 
the expansion, due to heating, forces air out and then at 
night the cooling causes the air left in the soil to contract 
and the reverse action takes place. Just how important 
this soil breathing is in the operations of tillage we do not 
know. Its amount will be increased or diminished as we 
increase or diminish the porosity of the soil and as we 
modify the conditions which affect the diurnal changes of 
temperature. 

100. Eifect of Atmospheric Pressure on Soil 
Water. — When soil is nearly saturated with water, air 
can neither enter nor escape from it readily except where 
large openings or passages exist. In consequence of these 
facts, when the air pressure over a region becomes less 
the springs of such regions often discharge more water 
and the water may. stand higher in the wells. The air 
confined in the soil and unable to escape rapidly, expands 
when the pressure falls and forces ' the water toward any 
openings which may exist. The reverse action also takes 
place when the air pressure increases, causing the water 
in the wells to be depressed and the same springs to dis- 
charge more slowly. "Blowing wells" owe their character 
also to the changes in atmospheric pressure. 



57 

101. The Suction Pump. — The common pump isone 
of the applications of atmospheric pressure. It should be 
understood, however, that the pressure of the air is in no 
way a source of power; it originates no part of the energy 
expended in pumping. Practically the only part the air 
plays in pumping is that of crowding the water up into 
the cylinder of the pump after the lifting of the piston 
has removed the pressure from the water in the suction 
pipe. The height to which the atmosphere will sustain a 
column of water at sea level is thirty-fcur feet; but a pump 
producing a perfect vacuum could not raise water to that 
height on account of the downward pressure exerted by 
the vapor of water and the air contained in water rising 
into the vacuum formed by the pump and exerting a pres- 
sure downward upon the column of water raised." Com- 
mon pumps are necessarily so imperfect in their action 
that it is found impracticable to have the suction pipe 
longer than sixteen to twenty feet above the water to be 
raised. 

102. Size of tlie Piston. — The amount of water dis- 
charged by a suction pump is determined by the length 
of the stroke and the area of the piston ; and these in turn 
are determined by the strength of the pumping force and 
the depth of the well. In working a common pump a man 
can exert a pressure of only fifteen to twenty pounds 
comfortably upon the pump handle, and as the power-arm 
of the lever is only from five to seven times the length 
of the weight-arm the weight of water which can be lifted 
at one stroke cannot much exceed seventy-five to one hun- 
dred pounds. This being true, it is evident that pumps 
to be placed in deep wells must have smaller pistons than 
those placed in shallow ones. It was shown in 88 that 
the pressure of water is proportional to its depth, and in 
89 that water forty feet deep exerts a j^ressure of two 
thousand four hundred and ninety-six pounds per square 
foot when at a temperature of 50° F. , or at the rate of 
seventeen and one-third pounds per square inch, and hence 
tne area of the piston for the pump to lift water forty 
feet should not exceed 

--7^-^ = 5. ( 8 square inches, 

J. i . o 

and this is given when the diameter of the piston is 2.7 



58 

inches. On account of the friction of the piston and of 
the water in the pipe and of the inertia of the water, a 
piston of that size would work hard in a well of that 
depth. In a well where the water is to be raised only- 
twenty feet the area of the piston could be twice, and for 
ten feet four times, as great respectively; these would be 
given by diameters of 3.8 and 5.4 inches; but, as in the 
first case, they are too large for easy action. Three inches 
would be large for twenty feet. 

103. Rate of Pumping. — The rate of discharge by a 
pump will be governed by the area of the piston, the 
length of the stroke and the number of strokes per minute. 
If the area of the piston is five square inches, the length of 
stroke five inches and the number of strokes per minute 
forty, then 

5 X 5 X 40 = 1,000 cubic inches 

or 4.3 gallons per minute. 

104. Function of Air Chambers. — In all single-act- 
ing pumps the power is able to do useful work on the 
piston only when it is moving in one direction. In deep 
wells, where a long coluinn of water must be quickly set in 
motion and then allowed to come to rest again, the intermit- 
tent action of common pumps is a serious objection, and to 
avoid this, air chambers are sometimes attached. The 
principle of their action will be understood from a study of 
Fig. 26. 

The air in the upper portion of the chamber, which can- 
not escape, is compressed by the rapid action of the piston 
and then during the reverse movement, it gradually re- 
gains its original volume, forcing the water out in a nearly- 
continuous stream. The water, therefore, is obliged to flow 
with only one-half the velocity of that which would be re- 
quired with no air chamber, and consequently a pump 
having an air chamber properly placed can be worked by a 
wind-mill in a lio-hter wind than one without the air chamber. 
The air chamber attached commonly to pump stalks has no 
influence on the pumping except when the pump is used to 
force water above the lev-el of the air chamber. To render 
the greatest service, an air chamber should be placed at as 
low a point as practicable in the well where there will be 
but a short column of water between the piston 'and the 
air chamber. 



59 




Fig. 26. 



60 



105. The 8ipllOli. — The flow of water through the 
siphon IS maintaiDed by a force represented by the difference 
in pressure in the two arms, the siphon being kept full by 
atmospheric pressure. The action of the siphon is ex- 
plained as follows : 

a^ 







Fig. 27. 

When the siphon is filled with water the downward 
pressure in the short arm is due to the upward pressure 
of the air at d, Fig. 27 and the downward pressure of the 
column of water a b, which, using the values in the figure, 
gives a total of 

2 + 24- 14.72 = 18.72 

The downward pressure in the long arm of the siphon is 
equal to the downward pressure of the column of water a d 
and the downward pressure of the air on the water in the 
vessel, or 

(6x2) -I- 14.72=26.72. 

As the two air pressures are equal and in opposite direc- 
tions they balance each other, leaving the force which de- 
termines the flow the difference in the pressure of the two 
columns of water, or 

12 - 1=8. 

It is evident that the greater the difference in the length 
of the siphon arms the greater will be the velocity of dis- 
charge. 

106 The Flow of Water. — When liquids move in a 
stream the molecules do not become separated from one an- 



61 

other to any appreciable extent. The stream moves as a 
whole, the density of the liquid remaining the same in all 
its parts. 

The flow of fluids is caused by a difference of pressure 
within the mass caused either by increasing it at some 
point or by diminishing it at another. Small velocities 
are associated with small differences of pressure and large 
velocities with large differences. 

107. ^^Head of Water."— The velocity with which 
water issues from an orifice in a vessel is due to the pres- 
sure of the liquid above the center of figure of the orifice 
and this distance is called the head. If it were not for the 
viscosity of the water, and the resistance offered by the 
orifice itself, the velocity would be equal to that which a 
body falling in a vacuum would acquire in falling through 
the distance equal to the head. This is expressed by the 
equation 

Velocity— j'2gH 

where H is the head and g is the velocity the force of 
gravity is able to produce in a falling body during a second 
of time and is equal to 32.2 feet. If the head is ten feet, 
then the velocity of discharge, leaving resistance out of 
consideration, would be 



Velocity= \ 2 x 32.2 x 10=25.3. 

What would be the velocity of discharge with a head of 
two feet? four feet? six feet? eight feet? twelve feet? 

108. Flow of Water in Pipes. — The quantity of water 
discharged by pipes is very much modified by their diam- 
eters, lengths, degree of roughness, and by the presence 
or absence of curves or angles. Other things being the 
same, the greater the head the greater the discharge; the 
greater the length and the less the diameter the less 
the discharge ; the greater the number of bends or angles 
the less the discharge. 

Tnere is no simple rule for computing the amount of 
water a pipe of a given length and diameter will discharge 
under a given head. To compute the discharge exactly 
the velocity of discharge at the moulh of the pipe and the 
area of its openings are required. AVhere the pipes range 
from .75 inch to six inches in diameter, and their lengths 



62 . 

lie between two hundred and two thousand feet, the equa- 
tions beluw^ give the velocity in feet per second, but with 
only a rough degree of approximation, 

m in^feet _ ^pi/ ^"^ Q ^ PiP^ ^^ ^ ^ ^^ ^ h ead in feet 
per second length in feet + 54 x diam. in feet. 

This may also be expressed as below, the dimensions all 
being in feet : 

1600 X diam. pipe x head 
length + 54 times diam. 



(2) Square of velocity in feet per second: 



In case the lengl^h of the pipe is twelve hundred to two 
thousand times the diameter, the factor fifty-four times di- 
ameter may be omitted without affecting the result very 
much. In such cases if the diameter and head are ex- 
pressed in inches the velocities may be more readily de- 
termined by the following: 

1600 x diam. x head 
^^^ ^"— 12 X 12 X length. 

If the diameter of a pipe is two inches, its length two 
hundred feet and the head four feet, what is the velocity 
of discharo-e? 



By (1), v=40|/ T2 X 4 ^ 40^/ Ta .-^2.259. 

•^ ^' » 200 + 5iXx% ^ ^fi^ 

1600 X Xx4: 
By (2),V-^ ,,Q^ 5-^^ ^-5,103-; 

whence, v^2.259 ft. per second. 

1600 X 2 X 48 
By ^^)-^ - 12x12x200 -^ 333; 

whence. v=:2.309 ft. per second. 

The last formula gives a velocity of .05 feet per second 
too large. 

What is the velocity of discharge when the diameter of 
the pipe is six inches, length two thousand feet, head four 
feet? 

To find the discharge of water in cubic feet per second, 
multiply the velocity in feet by the area of a cross-section 
of the pipe in feet. 

Discharge = velocity x area of opening. 



HEAT. 



109. Nature of Heat.— Heat is a form of molecular en- 
ergy. When a hot body is brought into contact with a 
cold one, the molecules comprising the hot body have their 
velocities slowed down by collision with the slower-moving 
molecules of the cold body and energy is transferred from 
the hot body to the cold one ; and, if the contact continues, 
the transfer will go on until the molecular energy, per 
unit of weight, is equal in the two bodies. If a hot' ball 
of iron is allow^ed to cool in the air, the cooling is the re- 
sult of the ball doing vmrk on the air. The molecules of 
air which come in contact with the surface of the ball are 
struck by the molecules of the ball and made to move awav 
with a higher velocity than they had before, just as a 
ball approaching a bat is struck by it and flies to field 
leaving the bat motionless, a nearly complete transfer hav- 
ing taken place. When a cold iron is thrust into the forge 
fire a part of the energy of the molecules of the burning 
coal and of the products of combustions is transferred, by 
collisions, to the molecules of iron, and the temperature of 
the iron rapidly runs up. 

110. Solar Energ-y.— When the sun rises the tempera- 
ture of bodies uj3on which it shines becomes higher as a 
rule, and when it sets the temperature again falls, and, as 
a rule, continues to do so until the sun begins to 'shine on 
them again. So too, as our days grow longer and longer 
with the approach of summer, the mean daily temperature 
becomes higher, and then falls away again as the nights 
become longer than the days. Such, and many other facts, 
prove that the sun is a source of energy, and that in some 
manner this energy is being transferred to the earth. 
Since the earth travels entirely around the sun once each 
year, and yet each day receives energy from it, it follow^s 
also that solar energy is leaving the sun continually in all 
the directions in the plane of the earth's orbit, and is in 
fact traveling away in every other direction. 

111. How Solar Energy Reaches the Earth.— When 
one stands on the shore of a small lake and aa'itates its 



"to 



64 

waters in any manner, waves start out from the place of 
disturbance, traveling in all directions toward the bottom 
and the distant shore lines. When these waves reach the 
bottom, the shore and the air resting upon the lake, they 
lose a part of their energy, the lost portion being trans- 
ferred to whatever foreign medium is struck by them. 
The energy generated in the muscles of the persou agitat- 
ing the water is thus conveyed away from him in all di- 
rections, and, sooner or later, is changed into the energy 
of molecular motion known as heat. The person is there- 
fore a source of energy, which is borne away from him in 
the form of waves in the water and air, and this v^ave en- 
ergy becomes changed to heat, and thus the person in a 
small degree warms the pebbles lying on the distant mar- 
gin of the lake, not by the heat of his body, but by the 
waves he set up in the water. It was not heat which 
traveled to the distant shore, but water waves which, 
striking the sands and pebbles, gave a part of their en- 
ergy to be transformed into energy of heat in them. 

The sun is wholly immersed in a cold medium called 
ether and the molecules of the sun's surface beating against 
this have their energy transformed into waves in it which 
travel away in all directions just as waves of water spread 
away from a disturbing body in it, but at a very much 
more rapid rate, the velocity being one hundred and eigh- 
ty-six thousand six hundred and eighty miles per second, 
a speed which brings* them to us in about eight minutes 
after their origin at the sun's surface. Sir Wm. Thomp- 
son estimates that the sun is constantly doing w^ork upon the 
ether at its surface at the rate of one hundred and thirty- 
three thousand horse power for each square meter of its 
surface, and the ' 'mechanical value of a cubic mile of sun- 
shine" near the earth is placed at twelve thousand and 
fifty foot-pounds, and, as this energy is approaching us at 
the rate of one hundred and eighty-six thousand six hun- 
dred and eighty miles per second, the a.mount which falls 
upon a square mile of the earth's surface in that time is 

186680 X 12050 ft.-lbs.=2249494000 ft.-lbs, 

and this is equivalent to about eighty foot-pounds per square 
foot each second. 

112. Kinds of Ether Waves. — The molecular oscilla- 
tions or vibrations at the sun's surface are not all of them 



65 

at the same rate and hence they set up waves of different 
frequencies of vibration in the ether, the slowest known 
being at the rate of one hundred and seven billions of 
thrusts upon the ether each second and the most rapid at 
about the rate of forty thousand billions per second. When 
the wave frequencies lie between three hundred and ninety- 
two billions and seven hundred and fiftj'--seven billions per 
second, such waves, falling in the eye, produce the sensation 
of light and we speak of them as light leaves. Waves slower 
than three hundred and ninety-two billions per second pro- 
duce no sensation of light in the eye, but when absorbed 
by the skin they cause the sensation of warmth and are 
called dark heat vKives. Waves more rapid than seven 
hundred and fifty-seven billions per second, when they fall 
upon 1he molecules of a photographer's plate, or upon a 
living green leaf, set up such intense vibrations in these 
molecules as to break them down, producing chemical 
changes and hence these are called chemical /raves. It 
should, however, be kept distinctly in mind that there is 
no light, no heat and no chemical action until the ether 
waves have dashed against some molecular shore and have 
been wrecked upon it. When any of these waves fall upon 
what we call a ^/acA* substance, like a thick layer of lamp- 
black, they are nearly all absorbed and the body becomes 
heated. On the other hand, when they fall upon a pure 
irhite substance, like snow, the waves rebound with nearly 
their full vigor and there is very little of either heating or 
chemical effect. When the waves fall upon what we call 
green substances, like the chlorphyl of growing leaves, most 
of the chemical waves and a portion of the light waves are 
wrecked by it and the chemical changes natural to grow- 
ing leaves are the result. 

113. Work Done on the Earth by the Ether Waves- 
It was stated in HI that eighty foot-pounds of energy per 
square foot reach the earth's surface each second. This 
seems like an enormous amount of work when it is fio-ured 
in horse power for a section of land, the amount being 

2249494000 

550 "^ ^089989 horse power, 

and it is difficult at first to realize that it can be true. 
To comprehend the situation we need to know that the 
earth is traveling through a cold region having a temper- 



6Q . 

ature of absolute zero, or — 273° C, with only the thin 
atmosphere to protect it from that cold. If the mean an- 
nual temperature of Wisconsin is 45° F. or 7" C, its tem- 
perature is maintained by the sun at 

273° -f 7° = 280° C. 

higher than that of the space which surrounds it. The 
earth is therefore rapidly sending ether waves back again 
into space, and thus a large part of the energy w^hich 
comes to us is lost. The motions of the air, and of the 
water in the ocean and to and from the land, represent 
other portions of this energy transformed. Most of the 
chemical changes occurring in growing vegetation repre- 
sent other transformations of solar energy, as do the ac- 
tivities of all forms of animal life; and when to these are 
added the chemical and physical changes in soils and 
rocks, due to it, it is plain that the amount needed to 
maintain the earth in its present state of activity is really 
very large. 

114. Transfer of Heat. — When one portion of a 
body is heated, as in the case of a poker thrust into the 
fire, the heat-energy gradually spreads to the distant end. 
This sort of transfer is known as co7iductio?}, and the rate 
at which it occurs is very different with different mate- 
rials. Metals and stone are among the best conductors, 
while wood, glass, water and woolen fabrics are among 
the poor conductors. The transfer of heat through air, 
where currents are prevented, takes place very slowly, 
and it is on this account that several thin garments are 
warmer than the same weight of the same material as a 
single garment. It is on this account also that sawdust, 
in the walls of buildings and about ice, is so serviceable. 
Hollow walls with dead air spaces utilize the same princi- 
ple, as does the practice of using one or more thicknesses 
of building paper in the construction of buildings which 
are designed to keep heat in or out. 

When heat is applied to the lower portion of liquids or 
gases the conduction of heat to portions of the mass causes 
it to expand and become relatively lighter than that not 
affected, and it is, in consequence, forced to rise, thus es- 
tablishing upward and downward currents. In such cases 
the heating is by conduction, but the heated mass is then 
transported, that not heated taking its place. The process 



67 



t 

2 

"i 

X 

I 

i 

z 
X 



Fig. 28. 



is named convection. The third method of transfer of heat 
is by radiation, and has already been described in 111. 

1 1 5. Draught in Chimneys. — The draught in chimneys 
is due to two principles, one that of convection, and the 

other that of asinration. In all properly 
constructed chimneys there is a draught, 
usually, even when there is no difference 
of temperature of air inside and out, and 
such draughts are strongest when the wind 
blows hardest. Why this is so will be 
readily understood from Fig. 28. The air, 
in its rapid motion across the top of the 
chimne)^, encounters the air molecules in 
its very top and forces them out and on- 
w^ard with it; this diminishes the weight of 
air in the chimney, and the pressure from 
below forces a new quantity into the mov- 
ing stream which in turn is driven away. 
The rapid forward motion of the outer air 
prevents it from descending into the space left by the air 
forced forward. When the fire is kindled the air in the 
chimney is made specifically lighter and is forced out on 
the principle of flotation ( 91 ). When the temperature of the 

air is raised one decree F. its volume is increased _L of its 

^ 491 

original volume, so that if air enters a stove at 70° F. and 
has its temperature raised to 234° F, its volume would be 
increased one-third and hence its weight diminished in the 
same proportion, and the relative weights of air per cubic 
foot inside and outside the chimney w^ould be as two to 
three. When these conditions exist, it is evident that the 
higher the chimney is the greater will be the difference in 
the weight of the two columns of air and the stronger the 
draught. When the chimney has its top considerably ex- 
tended above the surface it is placed in a region of more 
rapidly moving air cun-ents and the draft is made stronger 
on this account also. 

116. Transparency to Ether Waves. — When the 
hand is placed near a pane of glass, through which the sun 
is shining, the ether waves falling upon the hand are ab- 
sorbed and so increase the molecular motion of the skin, 
raising its temperature. The hand, in turn, sends out 
ether waves toward the sun, but they are of the long sort 



68 

and cannot pass through the glass, but are reflected back 
again upon the hand and join with those coming from the 
sun to raise the temperature to a still higher point. The 
glass is transparent to the short waves coming from the 
sun but opaque to the long ones into which they have been 
transformed in the hand. 

This is the principle upon which the hot-bed is 
constructed, which is practically an energy trap, allow- 
ing it to enter from the sun and then preventing its ready 
escape. 

On the same principle, too, large windows in the south 
side of dwelling-houses, especially if they are double, con- 
tribute a very large amount of heat toward warming the 
room in winter, and are really a great saving of fuel, be- 
sides contributing so much to healthfulness. The amount 
of heat which may enter a house in this manner during the 
winter is much larger than can enter it in summer, be- 
cause in winter the sun shines more perpendicularly upon 
the windows, which has the effect of making them larger, 
as explained in 173. 

Our atmosphere acts practically in the same manner to- 
ward the energy received from the sun and that radiated 
back again by the earth. It is highly transparent to the 
first and very opaque to the last. Clouds, fog and smoke 
are still more opaque to terrestrial radiations, and this is 
why frosts on a cranberry marsh or strawberry bed may 
sometimes be prevented by producing a cloud of smoke 
over it. 

117. Temperature. — The temperature of a molecule is 
an expression of the amount of energy it contains, and all 
molecules having the same temperatures are assumed to 
possess the same amounts of energy of motion. When the tem- 
perature of a given body is doubled its energy of molecular 
motion is doubled. Could the molecules of a body be brought 
entirely to rest, its temperature would be absolute zero, but 
this is a condition of things ver}^ difficult if not practically 
impossible to reach. 

118. Measurement of Temi)erature. — The common 
method of measuring temperature is by noting the changes 
in volume of a body which are associated with changes in 
its temperature. The material of a thermometer may be 
either solid, liquid or gaseous, and all three types are in 
use. For ordinary purposes the mercurial thermometers 



69 

are the best. The mercury expands more regularly than 
most other available liquids, thus making the graduation 
of the stem simple; it boils at a high and freezes at a low 
temperature; it can be readily seen and it responds quickly. 

The sensitiveness of the thermometer depends upon the 
relative diameters of the bulb and tube; the finer the bore 
of the tube and the larger the bulb the longer will be each 
degree. Too large a bulb is objectionable because a longer 
time is required for it to acquire the temperature of the 
body whose temperature is desired, and too fine a bore has 
the objection of not being readily seen. The long cylin- 
drical bulbs are better than the spherical ones because 
they present a larger surface and therefore respond more 
quickly, reaching a condition of rest sooner. 

119. Testing- a Thermometer.— The bulbs of most 
thermometers shrink after they are made, and if the grad- 
uation has been done before the shrinkage has occurred 
the reading of the thermometer will be found too high or 
will ultimately become so. To see whether the thermom- 
eter is correct, in this regard, it should be immersed in 
melting snow or crushed ice, from which the water formed 
by melting may readily drain away, and allowed to re- 
main until the mercury becomes stationary. 

If the thermometer is one of the dairy types, or has the 
bulb exposed, its correctness at blood heat may be deter- 
mined by placing the bulb under the tongue and keepino- 
the mouth closed over it for about one minute, reading the 
temperature while the bulb is yet in the mouth. If the 
person is well the thermometer should indicate about 
98.8*^ F. 

It is rarely true that the diameter of the tube of the 
thermometer stem is uniform throughout, there being a 
general tendency for the diameter to increase from one 
end to the other. If the irregularity, of the tube is large, 
it may be correct at the freezing and boiling points and 
yet incorrect at intermediate points. If the tube grows 
larger from the bulb the same amount of expansion in the 
bulb will cover a shorter distance on the scale, and vice 
versa. Large inequalities in the tube may be detected by 
jarring the thermometer so as to separate a short column 
of the mercury, say three-fourths of an inch, and carefully 
measuring its length by divisions of the scale in different 
portions of the stem; if there is a large variation the 



70 " 

length of the column separated will vary as it is moved 
from place to place. 

120. Kiiuls of Thermometer Scales. — There are two 
scales used in this country, the Fahrenheit and Centigrade. 
The first places the freezing point of water at 32"^, and the 
boiling point at 212°, the second at 0° and 100° respect- 
ively. The Fahrenheit scale, between 32° and 212°, is 
divided into one hundred and eighty divisions called de- 
grees, while for the Centigrade scale the number of divis- 
ions is just one hundred. This being true, 

180' Fahr.= 100 Centigrade. 

- , , ^ 100 5° 
andrF.=jg^=-^C. 

,,,^ 180 r^ 
andra=^^-^^^F. 

To convert the readinocs of a Fahrenheit scale into Centi- 
grade degrees find the number of Fahrenheit degrees from 
the freezing point and multiply this by |. 

5 

No. of degrees F. from freezing x-^=ISro. degrees C. 

To convert Centigrade degrees into degrees Fahrenheit 
multiply the number of degrees by f and the result will 
be the number of degrees F. above or below 32° F. 

9 
No. of degrees C. x-p=No. of degrees F. above or below 32' F. 
o 

121. The Heat Unit. — It requires sixteen times as 
much heat to raise the temperature of a pound of hydrogen 
one degree as it does a pound of oxygen, and other ratios 
are found to exist when other substances are taken. This 
makes it necessary to select a certain substance as a stand- 
ard when a unit of heat is desired. Water is taken as the 
standard and one heat unit is the amount necessary to 
raise a pound of water from 32° F. to 33° F. 

122. Specific Heat. — When the amount of heat which 
will raise the temperature of a pound of water from 32^ F. 
to 33" F. is applied to a pound of dry sand it will have 
its temperature raised through about 10° F. (Oelmer), or 
the same heat would raise the temperature of ten pounds 



71 

of sand one degree, and the speciiic hfjit of sand is said to 
be .1, that of water being 1. With the exception of hy- 
drogen, water possesses the highest specific heat known, 
and this means that it warms more slowly than do other 
substances; but the reverse is also true, and when once 
heated it cools more slowly or gives out a larger amount 
of heat. This is why large bodies of water make the 
winters of the lands adjacent to them warmer and the 
summers cooler. 

123. The Specific Heat of Soils. — Different soils, like 
other substances, have different specific heats, and hence 
warm at different rates under the same sunshine, and it is 
on account of this fact, in part, that one soil is warmer 
than another. In the following table are given the number 
of heat units necessary to heat one hundred pounds of water 
and of varieties of soils from 32° to 33° F. , and the tem- 
perature each would have after one hundred heat units had 
been applied to them at a temperature of 32° F. 

Table of Specific Heat or Dry Soils. 

No. of heat units re- Temperature of 100 

quired to raise lbs. after tlie ap- 

100 lbs. from 32" plicauon of 100 

1\ to 33"=' F. heat units. 

Heat units. Degrees F. 

Water 100.00 33.00 

Moor earth 22.15 36.51 

Humus 20.86 36.79 

Sandy humus 14.14 39.07 

Loam rich in humus. . 16.62 - 38.02 

Clayey humus 15.79 38.33 

Loam ]4.96 38.68 

Pure clay 13.73 • 39.28 

Sand 10.(18 41.92 

Purechalk 18.48 37.41 

These figures do not, in themselves, indicate the actual 
differences in temperature the several soils named would 
show under natural conditions because they are not only 
never perfectly dry but they have different capacities for 
holding water, and they differ also in their specific gravi- 
ties, so that one hundred pounds of one soil covers more 
surface, at a given depth, than another one does. We 
have not yet the data needed for an exact comparison, by 
volume, of the specific heat of soils. The higher the per 
cent, of water anv soil contains the more heat will be re- 



quired to raise its temperature one degree; so, too, the 
heavier the soil is per cubic foot the more heat will be re- 
quired to raise its temperature a given number of degrees. 
Sand has a less capacity for water than most other soils 
and is, on this account, naturally warmer, yet its higher 
specific gravity tends to make it colder than other soils. A 
cubic foot of dry sand weighs about one hundred and six 
pounds, while one of clay loam is only about seventy 
pounds. Saturated sand will contain, in the field, only 
about eighteen per cent, of water, while the clay loam may 
have as high as thirty-three per cent. Below are given the 
number of degrees one hundred heat units will raise the 
temperature of a cubic foot of sand and of clay loam when 
each is saturated with water, half saturated and dry. 

_, _ Saturated. Half saturated. Dry. 

Sand 3,4= y. 5°. P. 9.92° F. 

Clay loam 2.98° F. 4.49° F. 6.02° F*. 

Difference 42° F. .51° F. 3.9° F. 

It is thus seen that the greater weight of the sand, per 
unit volume, tends to offset the greater amount of water 
held by the clay, giving the two a more nearly equal tem- 
perature than they would otherwise possess. It will also 
be seen that the difference in the per cent, of moisture a 
soil may contain makes a relatively larger difference in the 
change in temperature a given amount of heat absorbed 
will produce. This is one reason why a well -drained soil 
is warmer than a similar one not so drained. 

124. ** Latent Heat." — When heat is applied to ice 
at a temperature of 32^ F., its temperature does not rise 
until the melting is completed, the whole energy applied 
being expended upon the molecules in moving them into 
new relative positions against the force of cohesion which 
binds them together in the crystalline arrangement of the 
ice. The amount of heat required to melt a pound of ice 
whose temperature is 32^^ F. is, in round numbers, one 
hundred and forty- two units, or enough to raise the tem- 
perature of one hundred and forty- two pounds of water 
from 32° to 33° F. This fact may be demonstrated approx- 
imately as follows : 

Take equal weights of water at 32'' F. and at 212° F. and 
mix them. The two weights of water will then be found 
to possess a temperature nearly equal to 



73 
212° -|-32° 



122° F. 



If, on the other hand, equal weights of water at 21 2^ F. 
and dry ice at ;J2<^ are placed together and the ice allowed 
to melt, the resulting water will be found to have a tem- 
perature of 51" F. The water has had its temperature 
lowered 

212°-51°=161° F. 
while the ice has had its temperature raised only 

51°-32'==19" F. 
Now if one pound each of ice and water w^ere taken for the 
experiment it is evident that the number of heat units 
consumed in melting the ice would be 

161-19=142 heat units. 

When w^ater has been raised to the boiling point no fur- 
ther increase of temperature can be effected so long as the 
pressure upon it remains constant, the whole amount of 
heat energy being now expended in converting the water 
into steam at the same temperature. 

If a pound of steam at 212° F. be condensed in 5.37 
pounds of water at 32^ F. there will then be (3.37 pounds 
of water having a temperature of nearly 212° F. The 
pound of steam in being converted into water has heated 
5.37 pounds of water through 

212^-32°=180° F. 
without having its temperature appreciably lowered. The 
molecular energy of the one pound of steam which was ab- 
sorbed by the 5. 37 pound of water was therefore 

180 X 5.37=966.6 heat units. 
This large amount of molecular energy in steam explains 
why a scald from steam is so much more severe than one 
from boiling water, and also why so small a quantity of 
steam, by weight, is required to cook a barrel of potatoes 
or feed. 

1 25, Evaporation ( ools tlie Soil.— We have seen that 
one pound of steam in condensing into water generates 
966. G heat units, and the reverse statement is also true, 
namely, to convert a pound of water into the gaseous 
state, under the mean atmospheric pressure, requires the 
absorption by that pound of 966.6 heat units. When one 



74 - 

pound of water disappears from a cubic foot of soil by 
evaporation, it carries with it heat enough to lower its 
temperature, if saturated sand, 32.8° F. ; and if saturated 
clay loam, 28.8° F. 

To dry saturated sandy soil until it contains one-half of 
its maximum amount of water requires the evaporation of 
about 9.5 pounds to the square foot of soil surface when 
this drying extends to a depth of one foot, while the simi- 
lar drying of clay loam requires the evaporation of 11.5 
pounds, and 

11.5-9.5 = 2 lbs. 

or the amount of evaporation which must take place in the 
clay loam to bring it to the same degree of dryness as the 
sandy soil. But to evaporate two pounds of water re- 
quires 

966.6 X 2=1933.2 heat units, 

and this, if withdrawn directly from a cubic foot of satu- 
rated clay loam, would lower its temperature 57.6*^ F. 
Here is one of the chief reasons why a wet soil is cold. 

That the evaporation of water from a body does lower 
its temperature may be easily proved by covering the bulb 
of a thermometer with a close fitting layer of dry muslin, 
noting the temperature. If the muslin be now wet, 
with water having the temperature noted, and the ther- 
mometer rapidly whirled in a drying atmosphere its tem- 
perature will rapidly fall, owing to the withdi'awal of heat 
from the bulb by the evaporation of water from the muslin. 

126, Regulation of Aiiiiiial Teinperatiires. — AH of 
our domestic animals require the internal temperature of 
their bodies to be maintained constantly at a point vary- 
ing only a little from lOO'^ F., and this necessity requires 
provisions both for heating the body and cooling it. The 
cooling of the body is accomplished by the evaporation of 
perspiration from the skin, and the amount of perspiration 
is under the control of the nervous system. When the 
temperature becomes too high, because of increased action 
on the part of the animal, or in consequence of a hio-h ex- 
ternal temperature, the sweat glands are stimulated to 
greater action and water is j^oured out upon the evaporat- 
ing surfaces and the surplus heat is rapidly carried away; 
each pound evaporated by heat from the animal withdraw- 
ing about 966.6 heat units. 



To 

127. Bad Kffeits of (old Kaiiis and Wet Snows on 
Domestic Animals. — Wlion ciittle. horses and sheej) are 
left out in the eold rains of our elimate the evaporation of 
the large amount of water which lodges upon the bodies, 
and especially in the long wool of sheep, creates a great 
demand upon the animals to evaporate this water. The 
theoretical fuel value of one i)ound of beef fat is 16,331 heat 
units, and that of average milk is 1,148 heat units. A 
pound of beef fat may therefore evaporate 

l??5i ^IG.8 lbs. of water, 
966.(3 

and a pound of average cow's milk 

^^i? =1.18 lbs. of water. 
966.6 

Od this basis, if a cow evaporates from her body four 
pounds of rain she must expend the equivalent of the solids 
of 3.39 pounds of milk. 

A wet snow-storm is often worse for animals to be out in 
than a rain storm, because in this case, the snow requires 
melting as well as evaporating, and the number of heat 
units per pound of snow is 

14*2.65 -h 966.6 = 1109.2o heat units, 

and the heat value of a pound of milk is barely sufficient 
to melt and evaporate a pound of snow. 

128. Cooling- Milk with lee and withhold Water.— 

If it is desired to cool one hundred pounds of milk fron 80° 
F. down to 40" F. it is practically impossible to do 
so with water in the summer season in Wisconsin. It is 
difficult even to cool it as low as 48"^ F., for most of the 
well and spring water has a temperature above 45° F. and 
much of it is above 50^ F. If lower temperatures than 48° 
F. are desired during; the warm season some other means 
must be resorted to. Since it requires one hundred and 
forty-two heat units to melt a pound of ice, one pound is 
capable of cooling from SO'' to 40° F. 

— J- — =3.75 lbs. of milk, 

supposing the specific heat of milk to be the same as that 
of water, which is not quite true. To cool one hundred 



76 

pounds of milk from 80° F. to 40° F. will require, there- 
fore, about 

^ ^_=26f lbs. of ice, 

supposing it to be used wholly in cooling the milk. 

If the water has a temperature above 40° F. before the 
milk and ice are placed in it, there will be required enough 
more ice to cool the water down to the temperature desired 
for the milk. 

The greatest economy in the use of ice will be secured, 
therefore, when the creamer contains just as little water 
as will cover the cans and give the reeded space for the 
ice, and when the walls of the creamer are made of so poor 
a conductor of heat as to admit as little as possible from 
without. 

129. Washing with Snow or Ice. — When ice or snow 
are used in winter for washing purposes there is a large 
loss of heat incurred in simply melting the ice and raising 
the temperature of the water from 32° F. up to 45° F., the 
temperature it may have in any well protected cistern. 
To melt a pound of ice and raise its temperature to 45° F. 
will require 

142-hl3=155 heat units. 

If three hundred pounds of water are required for a 
washing then the lost heat will be 

300 X 155=46500 heat units. 

The fuel value of one pound of water-free, non-resinous 
wood, such as oak or maple, has been found to be 15,873 
heat units; that of ordinarily dry wood, not sheltered, 
containing 20 per cent, of water, is 12,272 heat units. At 
this latter value it will require, supposing 50 per cent, of 
the fuel value to be utilized in melting the ice and heat- 
ing the water, 

2x46500 ^_,, - ,- 
— -„^„f. ^ ^i.oS lbs. of wood. 

more than would be needed to do the same washing with 
water at 45 "^ F. ; and if seventeen such washings are done 
during the winter the total cost for fuel would be the 
value of 

17 X 7.58=128 lbs. of wood. 



77 

to say nothing of the expense of getting the snow or ice 
and the unhealthfulness of handlino- it. 

130. Burning Green or Wet Wood. — Whatever water, 
wood or other fuel may contain when it is placed in the 
stove, so much of the fuel as is required to evaporate this 
water must be so expended and is prevented from doing- 
work outside of the stove. We have seen, 129, that when 
wood contains 20 per cent, of water there is required 

15873—12272=3601 heat units 

per pound of wood to evaporate the water contained, which 
is 22.7 per cent, of the total value. Wood, after being in 
a rain of several days, contains more water than this, 
and green wood much more, sometimes as high as 50 per 
cent., while well-seasoned sheltered wood may contain less 
than half that amount. 

It is frequently urged that when some green or wet wood 
is burned with that which is dry there is a saving of fuel. 
There is some truth in this, especially in stoves having too 
strong a draught and too direct a connection with the 
chimney and if the radiating surface is small or poor. The 
evaporation of the water prevents so high a temperature 
from occurring in the stove, which makes the draught less 
strong, and this gives more time for the heat to escape 
from the stove before reaching the chimney, and hence 
less is lost in this way. Then as the fire burns more 
slowly there is not the overheating of the stove, at times, 
which may occur with lack of care when very dry wood is 
used, and a considerable saving occurs in this way. These 
statements apply more particularly to heating stoves than 
to cooking stoves. Dry wood is best for the kitchen stove 
under most circumstances, the slower fire beino- secured 
when needed by using larger sticks and by controlling the 
draft. 

131. High Winter Temperatures Associated with 
Snow Storms. — "It is too cold to snow" is a common say- 
ing, but the truth is it cannot snow and remain very cold. 
Speaking in approximate terms, when a pound of water in 
the form of aqueous vapor in the air is converted into 
snow there is liberated 

966.6 + 142=1108.6 heat units, 
and, as the specific heat of dry air is only .2375, one heat' 
unit will raise the temperature of one pound of air through 



.2375 

and 4.21 pounds of air through 1° F. This being true, 
the freezing of one pound of aqueous vapor will liberate 
heat enough to warm through 1<^ F. 

1108.6 X 4.21 pounds=i667.2 pounds of air, 

and as water at 32° F. is 773.2 times heavier than air at 
the same temperature, the number of cubic feet of air raised 
1° F. must be 

r^r- =0/815.6 cu. ft. of air, 



62.41^ 



773.2 

which is equivalent to 5781.56 cubic feet raised 10° and 
to 1806 cubic feet raised from 0° F. to 32° F. When a 
snow fall of four to six inches occurs, over a large area, 
there is, therefore, a very large volume of air heated by it. 



PROTECTION AGAINST LIGHTNING- 



132. Natureof Electricity.— No very clear statement 
IS yet possible in regard to the real nature of either elec- 
tricity or magnetism, but the strongest evidence points 
to the conclusion that they are manifestations due to some 
action of the all-pervading ether which we have seen, HI 
is the medium through which energy generated at the sun's 
surface reaches the earth. In the battery, on the telegraph 
line, energy is generated by the chemical action there tak- 
-mg place and, by some action not yet clearly seen, the 
ether pervading the space between'' and surrounding the 
molecules of the telegraph wire conveys this energy t^o the 
distant stations, where it is absorbed by the receivino- in- 
struments and converted into mechanical motions which 
record or indicate the messages sent. In some manner 
the molecules of a conducting wire prevent the escape of 
energy to the outside ether as the walls of a speaking tube 
confine the sound waves developed in them, preventing 
them from being dissipated in the surrounding air and al- 
lowing them to travel to the end only slightly enfeebled. 

When a glass rod is rubbed with a piece of silk or fur 
the mechanical action develops a state in the ether of the 
rod which is shown by the ability of the rod, in this con- 
dition, to attract light objects to it. When a person 
speaks in front of a telephone the sound waves produced 
by the vibration of his vocal cords set the metal plate, 
near the end of the teleiDhone magnet, swinging in unison 
with the vocal cords, and the approaches and recessions of 
this plate so disturb the ether of the magnet as to cause 
It to take up a part of the energy of the vibrating plate 
and then to transmit it to the ether of the wire wrapped 
about the magnet and leading to the receiving station, 
where, by another of those wonderful yet universal trans- 
formations of energy, the action is reversed and the me- 
chanical swing of the plate in the receiving telephone 
gives back the words which set up the action at the send- 
ing station. 



80 



133. Atmospheric Electricity. — What the origin is of 
the intense electrical manifestations associated with thunder 
storms as yet lacks positive demonstration, but the close 
resemblances of these manifestations to the electrical man- 
ifestations developed by friction, when combined with the 
fact that the strongest atmospheric electrical displays are 
associated with the most violent air movements where 
rain or hail is present, has led to a general belief that 
this electricity owes its origin to the friction of the air 
currents upon the condensed moisture they are carrying. 
Fig. 29 represents the general character of an electrical 
discharge in the atmosphere. 




Fig. 29. 

134. Electrical Induction. — When a body, which has 
become charged with electricity, is brought near another 
body which has not been electrified it exerts an influence 
upon that body inducing electricity in it, and if the charge 
is sufficiently intense and the distance is not too great the 
electricity will break across from one body to the other, 
and the act may be accompanied by a flash of light and a 
report. 



81 

135. Positive and Negative Electricity. — It is im- 
possible to throw a stone into water, making a depression 
at any point, without raising a ridge around it which is equal 
in magnitude to the depression, but extending in the op- 
posite direction. When these two opposite phases are de- 
veloped they tend to come together, and the tendency is- 
stronger in proportion as the waves are higher. Somer 
thing analogous to this state of things seems to occure 
whenever and wherever electricity is generated. There 
appears always to be engendered two equal and opposite 
phases which tend to run together and obliterate each 
other unless prevented from doing so. The one phase is 
called positive and the other negative electricity. 

136. Conductors and Non-conductors of E lecric- 
ity. — There is a great difference in the ability of different 
substances to convey electricity from one place to another; 
those which convey electricity readily are called conduct- 
ors, and those which convey it poorly or not at all are 
called poor conductors or non-conductors. The metals 
generally are among the best conductors, and silver and 
copper are the best of these. Glass, gutta percha and 
dry air are among the poorest conductors. 

137. Discharges from a Point.— When a body be- 
comes charged with electricity the charge manifests itself 
only on the outside sui'face. If the body is a sphere the 
intensity of the charge will be uniform at all por- 
tions of the surface. If, however, the body is conical or 
has points upon it the charge will be most intense at the 
points, and if a discharge takes place it will occur first 
from the points, and it is this fact which has led to the 
placing of points on lightning rods. 

138. Wlien an Object May be Struck by Lightning.— 
When a cloud becomes so heavily charged that the air be- 
tween it and an adjacent cloud or an object on the ground, 
in which it has induced the opposite kind of electricity, is 
no longer able to prevent the electricity from breaking 
through, a discharge or stroke occurs. Usually the nearer 
the charged cloud approaches an object the more intense 
will be the charge induced by the cloud in the body ap- 
proached and the greater will be the chances of a stroke. 
The intensity of attraction increases as the square of the 
distance decreases, and this is why, when other conditions 



82 

are the same, elevated objects, like buildings, are more 
liable to a stroke than those which are lower. 

Buildings standing upon wet ground are more liable to a 
stroke than buildings in other respects similar but stand- 
ing upon dry ground, the greater danger coming from the 
possibility of a stronger charge being induced upon the 
house in consequence of the better conduction of the wet 
soil. Large trees near buildings have a tendency to pre- 
vent strokes. 

139. The Function of a Lightning-rod. — Lightning- 
rods have two functions to perform, the first and chief one 
being to discharge quietly into the air above, the electric- 
ity which may be induced upon a building as rapidly as it 
accumulates, and thus jore^;e?^/ a stroke from occurring ; and 
second, in case a stroke is inevitable, to diminish its in- 
tensity and convey to the ground quietly as much of the 
discharge as possible, thus reducing the damage to a 
minimum. 

140. Do Lightning-rods Afford Complete Protec- 
|;iQjj J — There is now a general agreement among physicists 
that properly constructed and mounted lightning-rods fur- 
nish a large protection to buildings; they are divided in 
opinion, however, as to whether complete protection is 
possible. The rod may be called upon to protect against 
discharges under two conditions: first, where a heavily- 
charged cloud comes slowly over the rod, giving it time to 
discharge the induced electricity and thus prevent an ac- 
cumulation; and second, where an uncharged cloud chances 
to be over a rod when it instantaneously becomes charged 
from some other cloud. When this occurs it is claimed by 
some that the rod has insufficient time to afford any mate- 
rial protection, and hence that it is hopeless to think of 
protecting completely against this class of cases. 

141. Essential Features of a Liglitning-rod. — For a 
number of years past there has been a fairly unanimous 
agreement in regard to the essential points of a light- 
ning-rod but some new discoveries in regard to the con- 
duction, of rapidly alternating currents, and in regard to 
electrical inertia, has led to a divergence again upon some 
points. It may be said that practically all are agreed 
that: 

1. The rod should be of good conducting material, contin- 



83 

uous throughout, terminating in several points above, and 
well connected with permanent moisture below the struct- 
ure in the ground. 

2. The rod should be in good connection with the building, 
especially with metal roof and gutters, and should be carried 
as high as the highest point of the structure to be protected. 

3. The points need not be very fine, but should be coated 
with some metal which will not rust. 

4. An iron rod, everything considered, is better and 
cheaper than one of copper, provided it is galvanized and 
of sufficient size. 

The fundamental point of disagreement at present is in 
regard to the form of the rod; some claiming that, if a suffi- 
cient area of cross-section is given the shape is immaterial so 
far as conducting ability is concerned, the solid round rod 
being the cheapest and most easily protected from rust; 
others maintain that the larger the surface the rod pre- 
sents the greater will be its conducting power aad that 
the flat ribbon is the cheapest and best. 

The first view is founded on the fact that, for steady 
currents, the conducting power is directly proportional to 
the area of the cross-section. The second view is founded 
upon what now appears to be the fact that very rapidly 
alternating currents travel only through an extremely thin 
layer of the surface of the conductor, and what also ap- 
pears to be the fact, that lightning discharges are a series 
of extremely rapid alternating currents. The settling of 
this point of dispute is likely to require the testimony of 
actual and extended practical tests with both forms of rods. 
142. Danger to Stock from Wire Fences.— The in- 
troduction of wire fences has to some extent incr-eased the 
danger from lightning to stock in pastures, owing to the 
tendency of the wires to become charged and then give off 
side sparks to the animals standing near. The danger is 
less from the barbed wire than from the plain, and the 
danger from both may be lessened by connecting the sev- 
eral wires with the ground by means of other wires tacked 
to the sides of the posts, the lower end being turned un- 
der the point of the post when set. The staples should be 
driven astride the two wires so as to hold them in close 
contact. It is not possible to say just how close together 
these discharging wires should be placed, but probably not 
nearer than 15 to 20 rods. 



SOIL PHYSICS. 



143. Nature of Soil. — The basis of all soil consists of 
the undissolved remnants of the underlying rocks. Asso- 
ciated with these remnants there is always a varying per 
cent, of organic matter, resulting from the decay of vege- 
table and animal remains ; a certain amount of dust par- 
ticles brought from varying distances by the winds, or 
washed down by rain-drops and snowflakes which have 
formed about those floating high above the earth's sur- 
face; and a considerable amount of saline substances 
brought constantly to the surface by the upward move- 
ment of capillary water, and left deposited when the water 
evaporates. 

144. Origin of Soil. — AH soils owe their origin to the 
processes and agencies of rock destruction which have 
been and still are taking place in three chief ways: 

1. Many rocks have been mechanically broken into 
larger or smaller fragments. 

2. Other rocks have had their molecules separated by 
simple solution as salt is dissolved by water, or the mole- 
cules have first been changed chemically and then dis- 
solved. 

8. Still other rocks have had some of their mineral con- 
stituents dissolved out, leaving the remainder as an inco- 
herent mass of fragments. In Fig. 80 are shown the stages 
of transition from the underlying rock to the soil above as 




Fig. SO. 
it occurs on limestone hills, while Fior. 31 shows the same 
facts for a more level limestone surface. On examining 



85 

the rocks of almost any quarry they are found to be di- 
vided into blocks of varying sizes by fissures or breaks 



SK^^'iB: 






Fig. 31. 

which owe their origin to a general shrinkage of the rocks 
and to movements of the earth's surface layers. These are 
the first steps in soil formation, and are plainly shown in 
Figs. 32 and 33. They exert a great influence in rock 
destruction and soil formation by furnishing easy access 
for water and the roots of trees to their interior, where 
the first by freezing and the second by growth expand and 
break the blocks into smaller fragments. Moving ice, in 
the form of glaciers, has done a vast amount of rock grind- 
ing, the present soil of all except the southwestern portion 
of our own state being the altered surface of a thick man- 
tle of boulders, gravel, sand and clay formed, transported 




Fort Danger, Wis. From a Photograph. 
After Chamberlin. 



Fig. SS. 



Bee Bhiff, Wis. From a Photograph. After 
Chamberlin. 



86 



and spread out by glacial action and the waters from the 
melting- ice. Then there are many animals which have 
contributed largely to 
this rock grinding and 
soil formation. Dar- 
win, through a long 
and careful study, 
reached the conclusion 
that in many parts of 
England earth-worms 
pass more than 10 
tons of dry earth per 
acre through t h e i r 
bodies annually, and 
that the grains of 
sand and bits of flint 
in these eai'ths are 
partially worn to fine 
silt by the muscular 
action of the gizzards 
of these animals : this 
same work is o-oinp' 
on in our own soils, 
where the holes bored 
by angleworms repre- 
sent the volume of 
dirt they have passed 
through their bodies. 
All seed-eating birds take into their gizzards and wear 
out annually large quantities of sand and gravel, after 
the manner of our domestic fowls. 

The other two methods of soil formation depend mainly, 
though not wholly, upon chemical changes wrought in the 
rock minerals. Pure water has the power to dissolve, 
without chemical change, greater or less quantities of most 
rock minerals which are brought to the surface by capil- 
lary action and become fine grains in the surface soil; but 
the larger part of this work is brought about by the ac- 
ion of water in conjunction with oxygen, carbonic, nitric, 
sulphuric, humic and other acids which it carries down 
into the rocks where the work of solution goes on rapidly. 
Mr T. M. Reade has estimated that the Mississippi alone 
carries to the sea annuallv 150,000,000 tons of rock in so- 




Fig. Sh. 



A tower-like casting ejected by a species of earth- 
worm, from tbe Botanic Garden, Calcutta: of 
natural size, engraved from a photograph. 
After Darwin. 



87 



lution, and yet a large part of the water which enters the 
soil is brought back again to the surface and evaporated, 
leaving the materials it has dissolved as a contribution to 
agriculture. 

145. Soil-COiivectioil. — On the surface of a lake the 
water which is at the top one moment is at another below 
the surface, the molecules changing position continually 
by convection currents due to changes of temperature. 
There is a movement somewhat analogous to this taking 
place in every fertile soil, though the movements are less 








1 



■1 



m 



o 



o 



^' .^ m 



Of Mm 



Fiij. 35. 

Section reduced to half natural scale, of the vegetable mould in a field drained anfl 
reclaimed 15 years before. Showing turf, vegetable mould without stones, 
mould with fragments of burnt marl, coal cinders and quartz pebbles. After 
Darwin. 

rapid and are due to different causes. Earth-woisms, ants, 
crayfish, gophers and various other burrowing animals 
each season bring large amounts of the finer portions of 
the lower soil and subsoil to the surface, forming systems 
of^ galleries with openings leading out to the free air at 



88 

various places. Each heavy rain, especially during the 
fall and spring, washes the finer surface soil into these 
galleries, filling them up, and new excavations are again 
made, thus keeping up a slow, but nevertheless a certain 
circulation, which in some of its effects is "like the fall and 
spring plowing, but much of it extending to far greater 
depths, the angleworms, ants and crayfish often going 
down from three to five or more feet during dry seasons. 
Darwin's, observations have shown that this rotation of 
soil, which he attributes largely to the action of earth- 
worms, tends to bury coarse objects, like flints, lying on 
the surface, as time passes, and in Fig. 35 is represented 
one of these cases as cited by him. 

l-l-O- Soil Kemoval. — Pitted against these processes of 
growth there is a })owerful and universal set of agencies 
constantly operating ever3^where to transport from higher 
to lower levels and from the land to the sea the surface 
soils, and the magnitude of this action has been estimated 
at not far from one foot each 3,000 years as an average 
for the whole land surface, and hence the superficial and ex- 
hausted soils are being slowly removed and replaced by 
new soil originating from the products of rock decay, 
and brought to the surface by capillary action and that of 
burrowing animals generally. The absolute amount of soil 
removal can be appreciated when it is understood that the 
summits of the bluffs represented in Figs. 36 and 37 show 
the a'eneral level of the surrounding' lower land at a former 
time and that, at times intervening between the present 
and that earlier period, vegetation has grown on soils oc- 
cupying all the levels between the two shown in the en- 
gravings. 

1-47. Surface Soil. — Soils proper comprise the sur- 
face live to ten inches of fields and woodlands generally. 
Oftentimes the depth of the true soil may be less than five 
inches, and then again it may exceed a depth of ten inches 
by varying amounts. It is the portion which has been 
longest and most completely exposed to the disintegrating 
and solvent action of rock-destroying agencies, and as a 
result of this fact it contains a smaller per cent, of the 
soluble minerals used by plants than the less altered sub- 
soil below. Its chief ingredients are: 

1. Saud. ) 

2. Clay. ]■ Composing about 90 to 05 per ct. of the dry weight; 

3. Humus. ) 



89 

which are commingled in varying proportions, giving rise 
to different varieties according as one or another of these 
ingredients predominates. The true soil, on account of 
its more complete aeration and its higher temperature, is 
the chief laboratory in which the nitrogen compounds for 
plant food are elaborated. 




Fig. 36. 

Giant's Casble, near Camn Douglass, Wis. 
From a Photograph. After Chamberlin. 



Fig. 37. 



Pillar Rock, Wis. From a Photograph. 
After Chamberlin. 



14:8. Kinds of Surface Soil. — For practical purposes 
soils are variously classified. When reference is had to 
the ease or dilBculty of working the soil it is spoken of as 

1. Light, or 

2. Heavy; 

but these terms have no si^'nificance as reo-ards actual 
weights; for a, sandy soil is spoken of as light, and yet it 
is the heaviest of all soils, bulk for bulk. The greater 
weight of the sandy soil is due more to the lack of large cav- 
ities which are found in the clayey soils, than to the higher 
specific gravity of the soil constituents. It is the greater 



90 

adhesiveness of the clayey soils which causes the plow, hoe 
or harrow to move with greater difficulty through them. 

When reference is made to the temperature of soils, at 
the same season, they are spoken of as 

1. Warm, or 

2. Cold. 

according as the temperature of the soil is relatively high 
or low. In this case the soils containing the greatest amount 
of water are, when other conditions are similar, the colder 
on account of the high specific heat, 123, of the water. 

When the chief ingredients of soil are the basis of dis- 
tinction they are frequently classified as 

Sand. Clay. Humus. 

Pen cent. Per cent. Per cent. 

1. Sandy soil, containing 80 to 90 8 to 10 1 to 3 

2. Sandy loam, " 60 to 80 10 to 25 3 to 6 

3 Loam " 25 to 60 25 to 60 3 to 8 

4; Clayey loam, " 10 to 25 60 to 80 3 to 8 

5. Clayey soil, " 8 to 15 80 to 90 3 to 6 

In peaty soils, or those of our low marshes and swamps, 
there is often as high as 22 to 30 per cent, of humus. It 
should be kept in mind that the sand, clay and humus of 
soils are not plant food proper except in a small degree; 
they are, except a part of the humus, what is left after 
the plant food is removed. They serve, however, an im- 
portant purpose in furnishing a proper feeding ground for 
the roots and a means of supporting plants in their up- 
right attitude. 

149. Subsoil. — The subsoil is the real source of the 
natural mineral constituents of plant food, while at the 
same time it acts as a reservoir for water which is deliv- 
ered at the surface by capillary action or held within its 
mass until the penetrating roots remove it. The depth to 
which roots penetrate the subsoil is really great, and I 
believe the depth is determined primarily by the water 
content of the soil, the roots traveling farther when the 
supply is scanty. Wheat roots are recorded as observed 
at a depth of seven feet in Rhenish subsoil of a sandy 
loam. Corn roots with us commonly reach a depth of 
three feet and often exceed four. It would appear, there- 
fore, aside from the fact that the subsoil is the parent of 
the true soil and that it acts as a water reservoir, that 
the chemical composition and physical characters of the 



91 

subsoil may determine in a large measure the productive- 
ness of land, unless it should be determined by future in- 
vestigations that the deep-running roots are simply water- 
gatherers. 

150. Yariatioii in ('()iHp()sitioii of Subsoils. — There 
is a marked difference in the composition of those subsoils 
of Wisconsin which are simply the residuary products of 
the decay of rocks in place, such as those represented in 
Figs. 80 and HI, and those which owe their origin to gla- 
cial grinding and mixing. This difference is clearly 
brought out in the table given below, which is compiled 
from analyses of typical samples of residuary subsoils 
from southwest Wisconsin and of glacial subsoils from the 
vicinity of Milwaukee as given by Chamberlin & Salisbury 
in the Sixth Annual Report of the United States Geolog- 
ical Survey: 

Rosidiiary (flacial Difl'er- 

Subsoils. Subsoils. ence. 

Per cent. Per ceyit. Per cent. 

Silica, SiO. 55.73 44.52 — 11.21 

Alumina, Al.. O, 18.16 8.01 —10.15 

Lime, CaO..'. . .■ ' 99 13.74 +12.75 

Magnesia, MgO 1.11 7.42 -[- 6.31 

Potash,K..0 1.24 2.48 + 1.24 

Phosphorus, P..O, 03 .09 +.06 

Carbon Dioxide, CO. 35 17.11 + 16.70 

Iron, Pe.,0, " 10.57 2.68 —7.89 

Organic matter 9.86 2.33 — 7.53 

Other substaaces 1 .37 1.95 +.58 

It will be seen that the insoluble sand, clay and iron 
compounds predominate in the residuary subsoils, while 
the lime, magnesia, potash and phosphorus compounds are 
in excess in the glacial subsoils, and this at lirst thought 
seems strange when it is remembered that the residuary 
soils are derived directly from magnesium limestones and 
that two of the four samples giving the average were 
taken in contact with th(» limestone itself, but these soils 
are what is left after the soluble carbonates are leached away. 

The photo-engraving of a relief map of Wisconsin, Fig. 
38, showing the glaciated and non-glaciated areas of the 
state, also shows, in general, the distribution of the glacial 
and residuary subsoils. The area of ruggcnl to})ography 
in the west and southwest of the state is the region cov- 
ered by the residuary subsoils. It should not be inferred, 



09 

t' -J 

however, that the composition of all of our glacial subsoils 
is fairly represented by the samples from the vicinity of 
Milwaukee, for in the northern portion of the state there 
were no large areas of limestone to be ground down by the 
ice to contribute the large amounts of lime and magnesia 
found in the locality cited. 




Fi(/. S6\ 

Photoengraving of a relief map of Wisconsin, showing the glaciated and non- 
glaciated areas oi the state. 

151. Size of Soil Particles.— The size of soil particles 
has very much to do with the value of a soil, this quality 
determining, in some measure, its water capacity, its re- 
tentiveness of fertilizers, its drainage, its aeration and the 
way in which the soil works. In general the relative num- 
ber of large grains as compared with the smaller ones is 
greater at the surface than at some depth below; this dif- 



93 

ference is due largely to the tendency of rain to pick up 
and carry away or to carry downward by percolation the 
finer particles. 

Chamberlin and Salisbury, as a result of their studies 
bearing upon the sizes of soil particles constituting resid- 
uary earths, say: "Out of 158,522 measured particles from 
several representative localities, only 929 exceeded .005 
mm in diameter. A fairly illustrative example from near 
the rock surface at Mt. Horeb, Wis., gave, in a single 
miscroscopic field, the following showing; 

Particles less than .00285 mm in diameter 15 , 152 

Particles between .00285 mm and .005 mm in diameter 208 

Particles more than .005 mm in diameter 54. 

None of the 54 particles reached so great a diameter as .01 
mm, '" that is, the largest of the 54 large ones had a diam- 
eter so small that 25,400 of them placed side by side 
would be required to span a linear inch. 

Many of the soils which tend so strongly to clog the 
plow are of this extremely fine-grained type, and a partial 
explanation may be found in the minute particles wedg- 
ing into the microscopic cavities due to the grain or text- 
ure of the material of the mold-board. 

152. Needs of Soil Aeration.— The necessity for a 
considerable circulation of air in the soil actively support- 
ing vegetation is generally recognized, and the demand 
for this circulation is three fold: 

1. To supply free oxygen to be consumed in the soil. 

2. To supply free nitrogen to be consumed in the soil. 

3. To remove carbon dioxide liberated in the soil. 
Prominent among the demands for oxygen in the soil 

may be mentioned: 

1. The respiration of germinating seeds. 

2. The respiration of growing roots. 

3. The respiration of nitric acid germs. 

4. The respiration of free-nitrogen-fixing germs. 

5. The respiration of manuie fermenting o-erms.' 

It has been abundantly demonstrated that when oxygen 
is completely excluded from seeds, placed under otherwise 
natural conditions for germination, growth does not lake 
place; if the germination is allowed to commence and then 
oxygen is withdrawn further development will cease. 
When the air surrounding a sprouting seed contains only 



94 

-i^ of the normal amount of oxygen the germination will go 
on, but the rate is retarded and a sickly plant is likely to 
result. Experience abundantly proves that when soil 
bearing other than swamp vegetation is flooded with water, 
or even kept in an oversaturated state, the plants soon 
sicken and die, and this, too, when they may be in full 
leaf and abundantly supplied with nourishment, sunshine 
and warmth. The difficulty is the lack of root-breathing. 
Oxygen in sufficient quantity cannot reach the roots to 
maintain life. The plants are suffocated. This explana- 
tion is apparently disproved by the fact that seeds of vari- 
ous kinds may be germinated in a float of cotton resting 
on the surface of water, and may even be made to mature 
seeds if the water in which the roots are immersed is kept 
supplied with the proper foods in solution. The floating 
gardens of the Chinese, consisting of basket-work made 
strong enough to carry a layer of soil in \vhich crops are 
matured with their roots immersed constantly in water, 
is another apparent disproof that wet soils kill the plants 
by depriving them of oxygen. The two classes of cases 
are, however, very different. In the cases of water cult- 
ure the free water is subject to strong convection and 
other currents which rapidly bring the water exhausted of 
its free oxygen to the surface, where it becomes charged again. 
In the water-soaked soil, with a relatively much smaller 
quantity of water, all possibility of convection currents is 
prevented by the cohesive power of the soil and the rate 
of diffusion in such cases must evidently be extremely 
slow, ?o that, viewed in this light, the two sets of cases 
stand in strong contrast. 

The natural nitrates, so essential to fertile soils, owe 
their origin to a minute germ closely related to the 
"mother of vinegar" and called in olden times the "mother 
of petre. " This ferment germ produces the nitric acid of 
soils which, after uniting with some of the bases contained 
in the soil, is absorbed by the plants as food. When the 
production of saltpetre was a considerable industry in 
Europe one of the conditions necessary to rapid formation 
was to keep the rich soil well aerated by frequent stirring 
and by the introduction of gratings to increase the air 
spaces. Oxygen is one of the essentials to the life of these 
important germs, and herein lies, in part at least, the ad- 
vantage of cultivation and of properly drained soils. 



95 

While we have, as yet, less positive knowledge in re- 
gard to the respiratory needs of the free-nitrogen-fixing 
germs, now coming rapidly into recognition, there is no 
reason to doubt the beneficial effects of a properly aerated 
soil upon them. 

In regard to the manure fermenting germs we have abun- 
dant proof of the need of ventilation from their action in 
the strong heating of the well ventilated coarse horse ma- 
nure when contrasted with the absence of heating in the 
close cow dung: free from coarse litter. 

Not only must oxygen and nitrogen be introduced into 
the soil, but the large amounts of carbon dioxide liberated 
by the fermenting processes and by the decomposition of 
the bicarbonates contained in soil-waters must be passed 
out in order to make room for the other gases to enter in a 
sufficiently concentrated form to answer the conditions of 
life going on there. 

153. Methods of Soil Aeration.— Most field soils, 
when in their natural undisturbed condition and nearly 
saturated with water, are impervious to such air currents 
as the greatest differences of atmospheric pressure and 
temperature in a given locality can produce. It is ^n this 
account, in part, that earth-worms come to the surface in 
such great numbers during and after heavy rains. The many 
perforations made by earth-worms constitute so many 
chimneys in and out of which the air moves with every 
change of atmospheric pressure and temperature. Culti- 
vation as soon as possible after rains aerates the soil at 
the time when it contains an abundance of moisture at 
the surface and is in the best possible condition for the 
rapid action of the nitre germs, which need plenty of air, 
moisture and warmth. 

Harrowing winter grain in the spring tends to make the 
aeration of the soil more perfect by breaking up the crust 
formed by the deposit of saline substances brought up by 
capillary action. 

Drainage, by carrying off the water more rapidly and to 
a greater depth, opens the pores of the soil, making its 
breathing more perfect. 

Strong-rooted crops, like the red clover, which send their 
roots deeply into the subsoil, leave it so channeled by the 
decay of those roots that a more perfect circulation of air 
is thus secured. 



06 

154. Soil Moisture. — The moisture contained in soils 
is of the utmost importance agricultuially, for without it all 
growth is impossible. Some of its chief functions may be 
stated as follows : 

1. By its solvent power it facilitates and promotes chem 
ical changes in the soil. 

2. By its expansive power when freezing it mechanically 
divides the coarser soil particles into finer ones. 

3. By its capillary movements it conveys food to the 
roots of plants. 

4. By its osmotic power it transports plant feed lohe 
leaves for assimilation. 

5. By the same power it conveys the assimilated food to 
the tissues for growth. 

6. By its osmotic power it swells the seed and ruptures 
the seed coats preparatory to germination. 

7. By the pressure it is under in the plant it gives suc- 
culent tissues much of their rigidity. 

8. By its high specific heat it prevents the soil temper- 
atures from becoming too high by day and too low during 
the night. 

155. Amoiiiit of Water Consumed by Plants, — Hell- 
riegel found, by experiments conducted in Prussia, that 
the amounts of water drawn from the soil and given to 
the air by various plants under good condition of growth, 
for each pound of dry matter produced by the crop in com- 
ing to maturity, were as stated in the table below: 

Number of Pounds of Water Transpired by Plants in Pro- 
ducing One Pound of Dry Matter. 

Water. Water. 

Lhs. Lbs 

Barley 310 Horse beans 282 

Summer rye 3o3 Peas 273 

Oats 376 Red clover 310 

Summer wheat 338 Buckwheat 363 

This, it will be seen, is at an average rate of more than 
325 tons of water for each ton of dry matter when grow- 
ing under the climatic conditions of Prussia. 

For Wisconsin the writer has found results given in the 
following table: 



97 



Number of Pounds of Water Required for One Pound of Dry 

Matter and the Number of Inches of Kain per Ton of 
Dry Matter. 

Water. Water. 

Lbs. Inches. 

Dent corn 309.8 2.64 

Flint corn 233 .9 2 . 14 

Clover 452.8 4 03 

Barley 392.9 3 43 

Oats 522.4 4.76 

Peas 477.4 4.21 

Potatoes 422.7 3.73 

The results in this table include not only the water 
which passes through the plant, but also that which was 
euajjorated from the soil upon which the plants grew ana 
hence indicate the amount of water the crops reported 
were able to use. These amounts, both for Europe and 
this country, seem enormous, but there can be no question 
but that the quantity needed is very large and necessarily 
so because practically all of the dry matter of the plant 
requires to be in solution when in ti'ansit to the place 
where it is finally deposited as a part of the structure. 

156. Position and Attitnde of the Water-TaMe.— 
The water-table is the surface of standing water in the 
soil. The distance the water-table lies below the surface 
exerts a marked influence upon the yield of crops per acre. 
If the water lies too close to the surface, drainage is re- 
quired to secure the best yields; when the water-table lies 




i,ni:i::'::iiili':iinuiuiirjii:iii 



',ii/mMifm/i/f/////j//wjwi/;///j// //im^^^^ 



Fig. 



AU 



too low, none of that water is available for plant growth. 
Permanent ponds and lakes are continuations of the 
water-table above the surface of the ground, and their 
levels lie at varying distances below the level of the water 
in the ground, the water-table rising usually as the dis- 
tance from these bodies of water increases and as the 
ground rises, as shown in Fig. 39. 




Fig. 40- 

Contour map of area occupied hv wells. Figures in lines give height of contours 
above the lake in feet, other figures indicate number of wells. 




Fig. J^l. 

Contour map of ground water surface on June -20. 1892. Figures in Hues give 
heights of contours above lake in feet; other figures indicate number of wells. 



10(1 ■ 

157. Wells and Groinid -Water. — There are very few 
localities on the earth where water can not be found be- 
neath the surface, but the distance varies between very- 
wide limits. Then, too, there are many localities where 
water-bearing layers are separated by those which are im- 
pervious to water and in which none is found. 

On the great majority of farms in our state the water 
supply of wells is that which percolates into the soils of 
the immediate or closely immediate neighborhood from the 
local rains and snows. 

The level at which this water can be found is generally 
farthest from the surface on the hio-hest o-round, and near- 
est to it on the lowest ground, but the level of the water 
under the high ground is almost always Jughe)' than that 
in the low ground ; and when the farm borders on a lake, 
it by no means follows that wells must be sunk to the 
level of this lake in order to procure water. On the 
campus of the university there is a well where the surface 
of the ground is 88 feet above Lake Mendota about 1,250 
feet distant, but the water in this well is some 52 feet 
higher than that of the lake. 

In Figs, -to and 41 are shown, by means of lines of equal 
level, the relation which standino- water in the a'l'ound 
holds to the surface above on the Experiment Station Farm 
and these serve to illustrate the kind of variations which 
occur in most localities where the surface of the ground is 
not level. It will be seen from these two plates that the 
water surface really has its hills and valleys like the land 
and in the same places but differing in relative height. 

158. The Loweriui*- of Water in Wells. — One reason, 
why the level of water in the ground rises as you go 
further back from the lakes and other natural outlets, is 
because the friction of the water in flowing through the 
soil increases the further it has to flow throua-h it, and 
this principle affects the supply of water in wells. 

When a new well is dug, and consider&,ble quantities of 
water are being pumped from it, it becomes a new drain- 
age outlet, and the surface comes to take the form indi- 
cated in Fig. 42, and the level of the water in the well 
takes a new height depending on the amount of water used 
and the rate at Avhich the water can flow through the soil. 

151). How to Big- Wells That Will Not Give Out in 
Dry Times. — Referring again to Fig. 42, it will be seen 



, 101 

that if the bottom of the well is at C, it is not possible to 
get as steep a slo})e down which the water can flow into 
the w^ell as would be possible if the well were sunk deeper, 
as at E, and hence during a series of dry years the general 
level of the ground water would become so low that the 
water must necessarily flow into the well very slowly, if 
at all, whereas with a deeper well it is possible to pump 
the surface down uQtil, by making the slope steeper, the 
rate of flow into the well remains constant, or nearly so. 



100 90 



1 so 70 CO 50 y 30 ^0 7f } ^^ .?[^ ^/^.-^/^ ^0 ^^y y ft?.y.^^ 




FUj. J,2. 

Showing the effect of pumping on ihe ground water surface. 

Whenever a well is to be dug, therefore, there should be 
made an estimate of the probable daily consumption of 
water from it, and the larger the demand is, the deeper 
the well should be sunk below the level at which water 
stands in it at first. The capacity of a well, like the capac- 
ity of a hay mow. is very greatly increased by adding a few 
feet to the bottom of it, and it never can be done as cheap- 
ly at any other time as when it is being dug. The dis- 
tance the bottom of the well should be sunk below the sur- 
face of the water will generally be greater the finer the 
soil is through which the water must flow in coming to the 
well. That is to say, if water is to be found in a coarse 
gravel the bottom will not need lowering as far as if it is 
found in fine sand or in clay with thin seams of sand or 
gravel. 

160. Percoliitioii of Impure Water into Wells. — 
There is a tendency, especially after heavv rains, for sur- 
face water to percolate into wells, and if the well is so 
situated with reference to the barn yards, the privy, or 
places where slops are thrown from the house or where 



102 



the drain from the kitchen leads into a dry well, there is 
great danger that the well water may be polluted by the 
rain taking up the surface impurities and carrying them 
into the well. In very wet times, when the soil is full of 
water at the surface, a well, whose walls are not water 
tight, furnishes an easy outlet into which the water drains 






1 v.* ' 



' • • • * (xir '-vjhich '', ■ H 




4 I {{{C 



»)^ 



' :' A If 's, scapin g V ''.'.• 



lirith ' confinel .'• ': .*• \ 
impede s\)mxiolatwn/. 






.' t • • 



0'^:'^>i''-';M 











ShowiuK the perco'atioQ of water into and out of wells. 

in the manner illustrated in Fig. 43, causing the water to 
rise rapidly, sometimes from one to three feet. In such 
cases the air in the soil below the very wet surface pre- 
vents the water from moving downward until the air can 
first escape and open walled wells furnish an easy escape 
for the soil-air at such times, and this results in the water 



103 



following the soil-air into the well as shown in the figure. 

Wherever it is practicable to do so, farm wells should 
be provided with water tight curbing of some sort extend- 
ing either to the water or to the rock in case that is struck 
before water is reached. 

From the standpoint of pure water the five or six inch 
iron tubing now used in drilled wells and the smaller sizes 
used in drive-wells are among the best safeguards against 
surface contamination. 

Wells where the supply comes from nearer the surface 
than 10 ft. ought generally to be avoided as a source of 
drinking water. In such localities the well should be sunk 
deeper and the surface vein cut off by a water-tight curb- 
ing if it is practicable to do so. 




Fig. U- 

Showing changes in the surface of the water-table under alternate fallow plats and 
plats of growing corn The straight lines connect the water-levels of wells 1 
and 7 on the dates specified at the right, and the broken line joins the water 
surfaces of wells 5?, 3, 4, 5 and 6 on the same dates. 

161. Fluctuations in the Level of the Water-Table. 

— The level of the water in the ground is not constant, but 
stands higher after a series of wet years and falls again 
with a succession of dry seasons. There is also an annual 
rise and fall of the water-table, the water standing lowest 
toward the latter part of fall or early winter and highest 
in the spring. In those cases where the water-table lies near 
the surface it is frequently raised by single heavy rains. 
Even changes in atmospheric pressure affect slightly the 



KM. 

level of water in wells, causing it to rise with a falling 
barometer and fall with a rising barometer. 

The growth of crops appears also to affect the height of 
the water-table when it lies near enough the surface to 
come within range of root action. This effect is shown in 
Fig. 44. The same figure also shows to what extent 'the 
water-table fell during a growing season. 

162. Best Height of the Water-Table — It is a matter 
of great importance, as bearing upon all questions of land 
drainage, to know at just what distance below the surface 
of the ground the water-table should lie to interfere least, 
and at the same time to contribute most, to plant growth. 
In European cultivation it is held that the tillage of moors 
and bogs can only be successful when the water-table is 
maintained at least three feet below the surface in summer 
and 2 feet in winter. For light and gravelly soils in good 
condition a depth of 4 to 8 feet is held to be best for the 
majority of crops. The problem is manifestly a complex 
one which cannot be simply stated. The case must vary 
with the character of the soil, with the season, and with 
the habit of the cultivated crop, as to whether it is natur- 
ally a shallow or a deep-rooted one. 

163. The Yeitieal Extent of Root-Feediiig.— Just 
how deeply root-feeding may extend below the general 
limit of root growth must depend upon the vertical dis- 
tance through which capillary action is able to pass water 
upward into the root zone. In the fall of 1889 it was 
found that clover and timothy, growing upon a rise of 
ground some 2S to 30 foot above the water-table, had re- 
duced the water content of sand, at a depth of 5 feet, to 
4.92 per cent, of the dry weight, when its normal capac- 
ity was about 18 per cent., and this seems to be a case of 
strong root-feeding to a depth of more than 5 feet. 

In the table below are given the percentages of water in 
the soils of closely contiguous localities bearing different 
crops; the distance between the two most distant localities 
not exceeding; twelve rods and the o-rouiid nearlv level: 



105 



Showing Depth of Root-Feeding as Indicated by the Water 
Content of the Soil August 21, 1889. 

Clover ill Tiiuotliy and Com. Fallow 
Depth of Sample. Pasture. Blue Grass. Ground. 

Percent. Percent. Percent. Percent. 

0-6 in 8.39 6.55 6.97 16 28 

6-12in 8.48 7.62 7.80 17 74 

12-18 111 12. i2 11.49 11.60 19.88 

18-24 in.. 13.27 13.58 11.98 19 84 

24-30 in 13.52 13 26 10.84 18.56 

40-4:3 in 9.53 18.51 4.17 15.90 

Distance of lower sam- 
ple above water-table 2.36 ft. 1.97 ft. 2.12 ft. 2.22ft. 

This table shows clearly that root-feeding, in the case of 
both clover and corn, extended to a depth of at least four 
feet, and that the corn had fed deeper than the clover. It 
also shows that the timothy and blue grass had exhausted 
the soil moisture near the surface more than either of the 
other crops, but that the depth of feeding was less. 

The strong difference which is shown to exist between 
the amount of water in the fallow^ ground and the ground 
bearing crops shows in a marked manner the strong dry- 
ing influence of growing vegetation upon the soil. 

164. ( apacity of Soil to Store Water. —The rainfall 
of our state during the summer season is rarely enough to 
meet the demands of vegetation during the growing pe- 
riod, but the soil acts as a reservoir, retaining consider- 
able quantities of that which falls at other times. All 
soils, however, have not the same storage capacities,' and 
hence on fields receiving the same rainfall the water sup- 
\Ay for crops may be very unequal. 

Ivlenze makes the following general statements in re- 
gard to the water capacity of different soils: 

1. The saturation capacity of a given kind of soil in- 
creases as the size of the smallest particles decreases. 

2. The capillary capacity of a given soil containing only 
capillary spaces decreases as it is made more close and 
firm. 

3. The saturation capacity of soils is decreased by in- 
creasing the number of cavities which are larger than the 
capillary spaces. 

4. The saturation capacity of soil decreases as the tem- 
perature increases. 



lOG- 

In the following table are given the percentage and ab- 
solute capillary capacity of a section of soil 5 feet deep, 
as found by experiment, the soil being in its natural con- 
dition: 

Per cent. Pounds Inches 
of of of 

Water. Water. Water. 

Surface ft. of clay loam contained 32.2 23.9 4.59 

Second ft. of reddish clay contained. . . 23.8 22.2 4.26 

Third ft. of reddish clay contained 24 5 22.7 4.37 

Fourth ft. of clay and sand contained. . 22.6 22.1 4.25 

Fifth ft. of fine sand contained 17.5 19.6 3.77 



Total 110.5 21.24 

These figures show that the actual storage capacity of 5 

feet of soil is really very large, in the case in question, 

aggregating 

43560 .K 110.5 \,,..^^, 

7-—- =2406.69 tons per acre. 

2(00 

and this, at the rate of 325 tons of ^water per ton of dry 

matter, is sufficient, were it all availa,ble, to give a yield 

of 

2406.69 „ .__ , „ , . . 

-^- ==<-40o tons of dry matter. 
32d 

Fig. 45 represents the proportions by volume, of soil, 
air and water in the above section. 

The large storage capacity given to the soil in the last 
section will be found true only at very wet times, or 
where standing water in the ground is very near the sur- 
face. In all sandy soils, and probably in all others, the 
water slowly runs out downward and the more completely the 
farther the surface is from standing: water in the o-round. 
In Fig. 46 is shown both the method by which this fact 
was proven for sand and the distribution of water in it 
after all the water which would run out had done so. 
There it will be seen that the upper 6 in. could retain but 
1.93 per cent, of its dry weight of water while the lower 
6 in. retained 18.17 per cent., or more than nine times as 
much. 

165. Proportion of Soil- Water Available to 
Plants. — Not all the water which soils contain is availa- 
ble to plants, and considerable must remain unused if large 
yields are expected ; we have also seen that soil fully sat- 
urated is not in a suitable condition to produce crops. 



l4/'uteK 



Sell- 
Sec no. /t. 



Soil. 



Sell. 



rig. JfO. 

Showing the relative volumes of 
water, air and soil in the upper 
five feet of cultivated ground. 



36- 



2A 



IS- 



u- 



6- 



0- 



ZA4 



J,.ZS 



627 



1Z.3S 



is.n 



Fhf. Jf6. 

Showing method of determining the ca- 
pacity of long columns of soil for 
water, and its distribution. 



108 - 

Hellrieo-el concludes from observations of his own that 
soils give the best results when they contain from 50 to 
60 per cent, of their" saturation amounts, but this, I think, 
should be understood as applying strictly only to the up- 
per 12 to 24 inches of soil because, as the season ad- 
vances and the roots develop downward, the water of the 
subsoil is drawn upon gradually as it is needed, and the 
per cent, of saturation is reduced to the proper amount. 

During the season of 1890 Litch Dent and White Aus- 
tralian Flint corn grew side by side at the Experiment 
Farm in a light clay loam underlaid with sand, the soil 
containing at the time of planting 22.41 per cent, of 
water, and at the time of cutting 15.45 per cent., the mean 
saturation capacity being about 25 per cent. The Dent 
gave a yield of 9,875 pounds of dry matter per acre and 
the Flint 6,000 pounds. The amount of water lost by 
transpiration, evaporation aud drainage was at the rate of 
456 pounds of Avater per pound of dry matter for the Dent 
corn aud of 610 pounds for the Flint. 

An examination of the figures in 163 will show how 
completely crops may reduce the water-content of soil dur- 
ing dry seasons; those given there, for corn, being from 
the same locality as the above for the year 1889. 

!(>(». Kinds of Soils whicli Yield Their Moisture 
to Plants Most Completely. — The sandy soils yield their 
moisture to plants much more completely than do the 
clayey and other soils having a greater water capacity. 
This is clearly shown in 108^ where sand, at the bottom 
under the corn, contains only 4.17 per cent., wdiile the 
clay with sand mixed, in the second foot of the same sec- 
tion, contains an average of 11.79 per cent. The satura- 
tion capacity of the first is about 18 per cent., while that 
of the latter is about 26 per cent. The sand had given up 
more than three-fourths of its water while the clay still 
retained nearly one-half. 

If we compare the absolute amounts of water given up 
by each of the tw^o soils in question we shall find that the 
sand had yielded 13.83 pounds per cubic foot, while the 
clay had yielded only 12.5 pounds. It thus becomes evi- 
dent that w^hile the percentage capacity of the sand is much 
below that of clay its greater weight per cubic foot and 
the greater freedom with which it yields w^ater to plants 
makes its practical storage capacity for water, so far as 



109 

crops are concerned, nearly as great as the loamy clays. It is 
thus very clear that a sandy soil kept well fertilized has 
many advantages over the colder, less perfectly aerated and 
more obstinate clayey ones, which crack badly in excessively 
dry weather and become supersaturated in wet seasons. 

167. Movements of Soil Water.— The water in the 
ground is subject to at least three classes of movements: 

1. Those due to gravitation. 

2. Those due to capillarity. 

.3. Those due to gaseous tension. 

The direction of movement in each of these cases may 
be either: 

1. Downward. 

2. Lateral. 

3. Upward. 

The gravitational movements are the most rapid, most 
extended and belong to two types: 

1. Percolation movements. 

2. Drainage or current movements. 

The percolation movements are, as a rule, slower than 
the drainage movements and are usually downward, being 
only occasionally and locally upward; they consist of the 
slow filtering of water through the smaller soil pores. 
It is chiefly by percolation that all water finds its way 
into the ground. 

The drainage currents consist of those portions of the 
percolation waters which could not be retained in the sur- 
face soil by capillary action. They move like streams of 
water on the surface or like currents through pipes, giv- 
ing rise to springs and flowing wells. 

The capillary movements, 80 to 82, constitute the slow 
creeping of water over the surface of soil particles and 
root-hairs. In direction they are chiefly toward the 
surface of the ground and toward the root-hairs, during 
the time when these are in action ; but after showers there 
may be capillary movements downward provided there is 
unsaturated soil below, but even under these conditions it 
will not always occur. 

The gaseous tension movements originate in the changes 
in volume of the confined air due to changes of tempera- 
ture and of atmospheric pressure referred to in 99 and 1 61. 

168. Rate of Percolation. — The rate at which water 
percolates through soil varies with its character and 



no . 

physical condition. As a general rule the percolation is 
more rapid through the coarse-grained soils than it is 
through those of a finer texture, and it is on this account 
that sandy soils leach so badly. Clayey subsoils, especially 
if they are underlaid with sand, very often shrink and 
break into great numbers of small cuboid al blocks leaving 
numerous fissures between them which open down to the 
sand below ; through these a large amount of percolation 
may take place; and this effect is greatly intensified when 
the surface of the ground becomes cracked, as it often does 
when not prevented by cultivation. When in this condi- 
tion such soils may leach even worse than sandy soil. The 
perforations made by earthworms and other burrowing ani- 
mals also exert a considerable effect upon the percolation 
of water and the leaching of soils. 

In case a winter sets in with fall rains insufficient to sat- 
urate the soil and close up the shrinkage cracks and the 
channels formed by burrowing animals, considerable water 
finds its way into the ground after it has been deeply frozen. 
During the winter rains and thaws which occurred in 
1889, 1890 and 1891, there was a large amount of perco- 
lation on the Experiment Farm made evident by the alter- 
nate starting and stopping of the discharge of water in the 
tile drains. These facts have a significance in their bear- 
ing upon the practice of winter hauling and spreading of 
manure. 

16t). Rate of ( apillary Movement. —The rate of cap- 
illary movement in soils varies with the kind of soil, with 
the physical conditions, and also with the amount of water 
it contains. It appears to be more rapid in sand than it 
is in clay, and more rapid in clay containing humus than 
in that without. It is more rapid in a well firmed soil 
than in one possessing large pores. The degree of close- 
ness may, however, be so great as to impede the rate of 
movement. 

I have found that water may rise through 1 feet of fine 
quartz sand at a rate exceeding 1.75 pounds per square 
foot in 24 hours, and in a light clay loam at a rate greater 
than 1.27 pounds per square foot. In these cases, how- 
ever, the soil Avas devoid of all spaces except those pro- 
duced by the form and size of the particles, and the rate 
was measured by the amount of evaporation; but as the 
soil remained wet at the surface throughout the experi- 



Ill 

meat the possible capillary rates must exceed those stated 
by undetermined amounts\ I have found changes in the 
water-content of the soils of fields which indicate that, 
under these conditions, the rate of capillary movement, 
when the soil is wet, may exceed l.G(j pounds per square 
foot. 

When the soil is perfectly dry the rate at which water 
moves through it is relatively very slow, so slow that five 
cylinders of soil, each 6 inches in diameter and 12 inches 
high, standing in water one inch deep, and in a satu- 
rated atmosphere, required the intervals stated below for 
water to reach the surface in sufficient quantity to make it 
appear wet. 

In clay loam, time required to travel 11 inches G days. 

In reddish clay, time required to travel 11 inches 22 days. 

In reddish clay, time required to travel 11 inches 18 days. 

In clay with sand, time required to travel 11 inches 6 days. 

In very fine sand, time required to travel 11 inches 2 days. 

These are very fundamental facts in their bearing on 
the control of evaporation by surface tillage. 

170. Translocation of Soil-Water. — It frequently 
happens, in certain soils after rains and in most, if not 
all, soils after rolling or firming, that water is brought up 
into the surface stratum from the deeper layers; this 
change of position is named translocatioii and has impor- 
tant bearings upon questions of tillage. 

The translocation caused by rolling or otherwise firming 
the soil is due to the fact that reducing the non-capillary 
pores in soil increases its capacity for water and the rate 
at which water will move into it by capillarity, and this 
influence is sometimes felt to a depth of three to four feet. 
The deeper soil- waters may in this way, therefore, be 
brought to the surface or within the zone of root growth. 

The translocation caused by wetting the surface depends 
upon the principle that when the per cent, of water in a 
soil has fallen below a certain limit its ability to take 
water from another soil is decreased, and that when it has 
risen above a certain limit this ability is then diminished, 
that is, for each soil there is a certain water content at 
which the water enters it at the most rapid rate. It there- 
fore frequently happens that the water-content of the sur- 
face soil is below that at which water enters it most rap- 
idly, and when a rain comes which restores its strongest 



112 

« 
action again, water is also taken into it from the soil be- 
low so that the surface stratum may, in consequence of a 
rain, receive more water than actually fell, while the soil 
below is, by translocation, rendered actually drj^er than 
before the rain. This fact has an important bearing upon 
surface tillage immediately after showers, upon the trans- 
planting and watering of trees and upon questions of irri- 
gation. If the surface, after a rain, is allowed to remain 
undisturbed, the rapid evaporation which occurs in such 
cases may take away in a short time not only that which 
had fallen, but also that which was brought up by capil- 
larity from below, whereas simply stirring the surface, de- 
stroying the capillary connection below, would allow the 
surface onlv to drv and act as a mulch, retainino- the bal- 
ance in the ground for the use of the crop. 

171. Iiiiiueiice of Topography on Percolation. — The 
slope of the surface influences, sometimes in a marked 
manner, the percolation of rain-water and the water-con- 
tent of the soil. Whenever rains occur which are suffi- 
ciently heavy to cause water to flow along the surface, 
from the hill-tops toward the lower and flatter areas, less 
water is left to percolate on the highest sloping ground, 
while the more nearly level areas may have not only the 
water wiiich falls as rain upon them, but a portion of that 
which has fallen upon other ground. Nor is this all; as 
the water-table is generally higher under the high ground, 
156, there is a constant tendency for the water in the soil 
itself to percolate from the high lands toward the low 
lands, and so, when the water-table here lies within reach 
of root action, to increase the water supply for the season, 
sometimes to a disadvantageous extent, making drainage 
necessary, where in the absence of the high land it would 
not be needed. 

In those cases where the water-table under the high land 
is below the level of the surface of the low lands, and the 
low lands remain long over-saturated, there is a tendency 
for the w^ater to percolate toward the higher ground, but 
of course to return again at a later season. 

172. The Lossof Water by Surface Evaporation.— The 
loss of water by surface evaporation from the soil is very 
large during the early portion of the season and especially 
so if the surface of the ground is left long undisturbed. 
The writer has shown by experiments that a piece of un- 



113 

plowed ground lost, in early May, during seven days, 9.13 
lbs. of water per square foot from the upper four feet of soil, 
or at the rate of 1.304 lbs. per day. And also that a clay 
loam lost water in the upper three feet at the rate 
of 6.45 lbs. in one case, and 5.09 lbs. in another 
during four days, or at the mean rate per day of 
1.52 lbs. per square foot. During the present season, 
six cylinders each 42 in. deep, and 18 in. in diameter, 
w^ere tilled with soil saturated with water and placed in 
the open field, sheltered from rains by a canvas awnino- 
placed so as to allow about 12 in. of free space for the 
circulation of air over their tops; under these condi- 
tions there was evaporated from these surfaces an ao-o-re- 
gate of 226.7 lbs. of w^ater during 34 days from June 27, 
to July 31, or at the mean rate of .63 lbs. per square ft. 
daily, and this was in the shade. The first two ^gures 
given, 1.304 lbs. and 1.52 lbs. per day, give an average 
loss per acre of 30.75 tons of water daily by surface evap- 
oration when it takes place under the most favorable con- 
ditions, while the last figure, .63 lbs. represents a loss bj^ 
surface evaporation of 13.72 tons daily which is less than 
the average unless very careful and thorough tillage is 
practiced. 

At the larger figure, water is going away at a rate suffi- 
cient for nearly a ton of dry matter of corn every 10 days 
from each acre of ground, and at the slower rate still fast 
enough to consume in 100 days the water required for 4.4 
tons of dry matter of corn which is considerably more than 
an average yield in Wisconsin for the best farming. Sure- 
ly, then, here we have evidence ample to show that the 
careful husbanding of soil moisture is an essential part of 
successful farmino' in our climate. 

173. lullueiice of Topography Upon Eyaporation. — 

It is a matter of common observation that the south and 
southwest slopes of steep hills are often simply grass-cov- 
ered, while the north and northeast slopes may be heavily 
wooded. This difference of verdure is due largely to a dif- 
ference in soil moisture on the opposite slopes, which is 
determined chiefly by the difference in the rate of evapo- 
ration upon the two slopes. 

Other things being the same, the rate of evaporation, in 
our latitude, is greatest on hill-sides sloping to the south- 



114 



west and least on those sloping .to the northeast. Several 
conditions work in conjunction to produce this effect: 

1. More air comes in contact with windward than with 
leeward slopes, and as rapid changes of air over a moist 
surface increase the amount of water taken up, the evapo- 
ration is greater on the windward slope. 

2. Our prevailing winds, during the growing season, 
are southwesterly, and hence more air comes in contact 
with southwest slopes. 

3. Westerly and northerly winds are, with us, al- 
most always drier than easterly and southerly winds, and 
as evaporation is more rapid under dry than under moist 
air the westerly slopes are drier than easterly ones. 

4. Other things being the same, surfaces which are near- 
est vertical to the sun's rays receive most heat, and for 
this reason southward slopes, in the northern hemisphere, 
become most heated, and as evaporation takes place more 
rapidly at high than at low temperatures, southerly and 
southwesterly slopes lose most moisture from this cause. 
Fig. 47 shows how a surface inclined toward the south 



^ 


\ 


^ \ 


\ 




■ 


^.,^¥ 


^ 





Fig. J,7. 

must receive more heat per square foot than either the 
level surface or on the one inclined northward. If A65B 
is a section of a cylinder of sunshine falling upon the hill 
AEB, it is evident that A64E, the portion falling on the 
south slope, is greater than E45B, the portion falling on 
the north slope. It will also be evident that the 20-degree 



115 

slope receives more heat than does the 5-degree slope, and 
this more than the level surface. 

The effect of the wind upon the evaporation from the 
soil is at its maximum at the summit of a hill, because at 
this place the wind velocity is greatest, no matter from 
what direction it may be blowing. 

174. Effect of Woodlands on Evaporation. — A piece 
of woodland which lies to the southwest and west of a field 
exerts a considerable effect upon the humidity of the air 
which traverses that field, the tendency being to make the 
air more moist. Taking a specific illustration, the air on 
the leeward side of a second growth black-oak grove was 
found, on one occasion, to contain 3.3 per cent, more moist- 
ure than did that on the windward side at the same time; 
and again, when the wind was in the opposite direction, 
observations in the same localities showed 3.8 per cent, 
more moisture on the leeward side, the observations in the 
four cases being taken about 10 rods from the margin of 
the grove. There was observed at the same time a differ- 
ence of air temperature of 1.5'^ F., the leeward air being 
this much cooler in the field 10 rods from the grove, the 
width of the grove being about 30 rods and the trees from 
20 to 30 feet high. 



TILLAGE. 



175. The Objects of Tillage.— The chief objects of till- 
age may be briefly stated as follows: 

1. To destroy undesired vegetation. 

2. To place organic matter of various kinds beneath the 
surface where it will more readily ferment and decay and 
be brought within the reach of root action. 

3. To develop a loose, mellow and uniform texture in cer- 
tain soils. 

4. To control the water-content of soil. 

5. To control the aeration of soil. 152 and 153- 

6. To control the temperature of soil. 

176. The Destruction of I iidesirecl Tegetatioii. — In 
securing this object of tillage w^e have two classes of vege- 
tation to destroy, one, like the prairie grasses of a virgin 
soil or like the cultivated meadow grasses, which must be 
destroyed before there is root room for the desired crop, and 
the other which is designated by the general term of weeds. 

Plants spread out two broad surfaces, one in the air to 
obtain carbon dioxide, oxygen and sunshine, and the other 
in the soil to obtain water, nitrates and other food con- 
stituents. It requires but little study to reveal the fact 
that plants usually spread out their leaf surfaces in such a 
manner that each leaf shall be forced as little as possible 
to breathe the air of another leaf and that one shall shade 
another as little as possible. In a dense forest or thicket 
no fact stands out more prominently than the race each 
plant makes to outreach its neighbor and get into bright 
sunshine and free air. A study of root development shows • 
that the same law is followed beneath the surface. There 
are times of scarcity of food, and each root and rootlet 
tends to develop away from its neighbor into an unoccu- 
pied territory. Such facts teach, with abundant evidence, 
that there is no room for weeds in any soil where another 
crop is expected. 

When we remember that each pound of dry matter re- 
quires more than 300 pounds of water taken from the soil, 



117 

and that in most soils there is usually a scant suply of 
moisture at best, the importance of a weedless surface 
should be appreciated. 

The following definite case will serve to show how rap- 
idly weeds may consume the water of soil. 

On May 13, 1889, the water-content in the soil on ad- 
joining margins of a field just planted to corn an one of 
clover and timothy, was determined on the Experimen^t 
Farm, w^ith the results below: 

Corn groimd. Clover ground. 

Per cent, of ivaier. Per cent, of water 

Surface to 6 in. contained. 23.33 9.59 

12 to 18 in. coutained 19. 33 14.79 

18 to 24 in. contained 16 . 85 13 . 75 

These figures illustrate in a very forcible manner the 
great power vegetation has of withdrawing water from the 
soil, how naked tillage conserves it, and the importance, 
in all except the wettest seasons, of not allowing weeds to 
occupy cultivated fields. 

177. Plowing- in Organic Matter. — The decomposi- 
tion of most animal and vegetable tissues is the result of 
a growth in and upon thera of micro-organisms which, like 
all other living things, require a bountiful supply of moist- 
ure. Moisture is usually found in abundance at the sur- 
face in the shade of dense forests, but in open cultivated 
fields the stems of plants and coarse manures are too dry, 
most of the time, to maintain the life of micro-organisms 
unless they are buried a little distaace below the surface 
where the rate of evaporation will be checked, and where 
there is a better capillary connection between them and 
the water of the soil. In this condition, if the soil is 
sufficiently aerated so that the respiration of the life going 
on there is ample, the organic tissues are rapidly broken 
down and quickly become available as food for crops. 

178. Circnnistances which Modify the Time and 
Depth of Plowing in of Mannre. — We are yet a long 
way from being in possession of the rigid knowledge which 
is needed to make specific and exact statements regarding 
matters like these. There are some general statements, 
however, which may be helpful in practice if not followed 
too implicitly and without judgment. 

Coarse manures, when plowed in, tend at .first, to cut 
off the capillary connection with the soil-water below, and 



118 

where the plowing occurs in the spring, certain crops are 
liable to suffer from drought because of a lack of moisture 
in the surface soil; this is especially liable to be the case 
if the spring is dry. If heavy, soaking rains follow the 
plowing in of such manure, the soil particles are washed 
in between its straws and other litter and a good connection 
establshed between the surface and the soil below. This is 
what does happen usually in the case of fall plowing, and 
explains why on many, if not most, soils, the fall plowing 
in of such manures is preferable. It is evident that on 
soils naturally too wet, and especially in wet seasons, the 
spring plowing, in such cases, might be preferable. 

If manure is plowed in too deeply, and especially if the soil 
is close and fine, there is danger of too little air to permit 
of roapid decay, and the effects of manure under such con- 
ditions will be only partially felt the first season. 

If the soil is a leachy one, plowing the manure in deep- 
ly tends to increase the loss by underdrainage. 

179. Effect of Manures on the Water Capacity of 
Soils. — Humus stands foremost among the ingredients of 
soil in its power to retain capillary water. The barnvard 
manures, besides containing large quantities of saline fer- 
tilizers, contain much undigested vegetable fiber, which, 
when plowed into the soil, tends to decay into ordinary 
soil humus and thus to increase the water capacity of the 
lands to which they are applied; in this respect they have 
a superior value, when compared with most commercial 
fertilizers, esj^ecially if it shall be established that organic 
matter, in contact with dry earth, does oxidize with a loss 
of free nitrogen. 

180. The Importance of Good Tilth. — It is a gener- 
ally recognized fact that one of the chief objects of tillage 
is to produce a mellow seed-bed of uniform texture, and 
there are several desirable ends which are met wholly or 
in part, by good tilth. 

One of the strong recommendations of a rich sandy soil 
is found in the evenness of its texture and the lack of ad- 
hesion between its grains which permit of almost perfect 
symmetry in the development of roots and allows the root 
hairs to occupy most completely the soil interspaces. When 
this is true, not only is all the soil laid under tribute, but 
each and every rootlet, with its numerous root hairs, is do- 
ing full duty. If, on the other hand, the soil is uneven 



119 

and filled with hard lumps, a large portion of it is not 
only unavailable but it stands as a positive hindrance to 
root development, checking rapid root growth and making 
a much greater actual length of roots necessary in order 
to come in contact with a sufficient amount of soil. Noris 
this all; during the process of cultivation the lumps tend 
to work to the surface and become very dry; in this con- 
dition they absorb a large percentage of the suinmer rains, 
and, and as they are almost completely surrounded by free 
air, they give back this moisture to the atmosphere and 
thus prevent it from rendering any service. 

On the principle of oxidation of nitrogenous compounds 
with the liberation of free nitrogen the lumpy condition of 
soil should be expected to be a large source of loss of that 
important element of plant food. 

Mellow soil favors root-development in being easily 
crowaed aside by the expanding roots, and this is a mat- 
ter of some importance in all the succulent root crops, 
like beets, parsnips, turnips and carrots, for the actual soil 
displacement in an acre of these crops is very great, and the 
conclusion seems irresistible that a hard soil must mechan 
ically impede root-growth in such crops to a large extent 

A mellow, even textured soil is likely to be much better 
aerated than one not in this condition and better supplied 
with moisture also. 

181. Control of the Water-Content of Soils.— The 
operations of tillage aiming to control the water-content 
of soils proceed along one of three lines of action : 

1. To conserve the water contained in the soil. 

(a) By surface tillage. 

(b) By flat culture. 

(c) By mulching. 

2. To reduce the quantity of water in the soil. 

(a) By deep tillage. 

(b) By decreasing the water capacity. 

(c) By ridge culture. 

(d) By surface drainage. 

(e) By underdrainage. 

(f) By tree planting. 

3. To increase the quantity of water in the soil. 

(a) By increasing the water capacity. 

(b) By irrigation. 

(c) By firming the surface soil. 



12a 

182. Conseryatioil of Soil- Water. — On the great ma- 
jority of cultivated lands there is, as a rule, an insufficient 
supply of moisture to give the largest possible yield when 
other things are favorable ; and hence it becomes a matter 
of importance to check the evaporation from the soil sur- 
face and divert the water currents through the growing 
crop. 

183. Surface Tillage to Cheek Eyaporatioii. — In one 
of my experiments, where the rate of evaporation from the 
undisturbed surface of clay loam had been going on at the 
rate of .9 pounds per square foot in 24 hours, simply re- 
moving the crust of salts brought to the surface and de- 
posited there by evaporation, increased the rate of evap- 
oration to 1.27 pounds per square foot in the same time, 
and I found the same fact true for fine sand. These facts 
have a bearing upon the practice of harrowing winter 
grain in the spring, suggesting that the practice, may, in 
some cases, cause a waste of water. 

In the case of the fine sand referred to, the evaporation 
had been taking place at the rate of .91 pounds per square 
foot in 24 hours, just before the crust was removed; after 
its removal the surface was cut in small squares with the 
blade of a sharp knife held vertical to the surface, and then 
the rate of evaporation rose from .91 pounds to 1.75 pounds 
per square foot per day. On removing a thin layer of the 
sand, and replacing it immediately, the rate of evapora- 
tion fell to less than .5 pounds per square foot daily. It 
is thus shown that one form of surface tillage may increase 
the rate of evaporation while another form may check it in 
a very decided manner. 

A tool working like the disc harrow when the discs are 
running at a small angle, sim23ly slicing the surface as the 
knife did, increases the surface exposed to the air without 
destroying the capillary connection with the soil below, 
and tends to hasten rather than retard evaporation ; but if 
the tool completely removes a surface ' layer, leaving the 
ground covered with a layer of loose soil, a mulch is pro- 
vided which excludes the air, in a measure, and greatly 
retards evaporation. 

184. Iiiilueiiees of Early Spring Plowing. — A field 
test was made of the influence of early spring plowing in 
checking the loss of water from the soil. One piece of 
ground was plowed on April 28, and sowed at once to oats. 



121 

The amount of water in this soil was determined, in one- 
foot sections to a dei3th of four feet. Seven days later the 
water in this ground was again determined, and also in 
another strip lying immediately alongside of it which had 
not been plowed. The results showed that the upper foot 
of soil on the plowed ground had lost only 4.65 tons per 
acre ; and the other three feet had gained enough from be- 
low to leave the average unchanged, while the same depth 
of soil on the ground not plowed had lost 198.9 tons per 
acre. Nor was this all; the ground first plowed was in 
perfect tilth, while that plowed six days later had devel- 
oped in it such hard and large clods that it became neces- 
sary to go over it twice with a loaded harrow, twice with 
a disc harrow, and twice with a heavy roller, before it 
was brought into a condition of tilth even approximating 
what it would have had, had it been plowed six days earlier. 

It is evident, therefore, that the early stirring of 
soil in the spring not onlj^ saves the much-needed moisture, 
but it also prevents the formation of clods, a condition of 
soil which always greatly decreases Us productiveness. 

185. Effectiveness of Thin Soil Mnlclies. — Experi- 
ments have shown that even very thin mulches exert an 
appreciable influence on the rate of surface evaporation. 
As results of trials it was found that in still air stirring 
the soil to a depth of one-half inch gave a daily evapora- 
tion per acre of 5.73 tons as against 4.52 tons when stirred 
to a depth of three-fourths of an inch, while the undis- 
turbed surface lost water at the rate of 6.24 tons daily. In 
the case of mulching with fine air-dry soil the results showed 
a loss of 4. 54 tons per acre for a layer one-half an inch 
thick but only 2.4 tons when the layer was three-fourths 
of an inch thick as against a loss of 6.33 tons where the 
surface was not covered. These figures bring into strong 
relief the great effectiveness of even a thin layer of fine 
dry soil in checking surface evaporation and serve to em- 
phasize the importance of keeping soil in good tilth and of 
using tools which will leave the surface blanketed with a 
tine, even coat of soil. 

18(). Influence of Cnltivation on the Evaporation 
of Soil Water. — Experiments in the field on fallow 
ground have shown that frequent cultivation as compared 
with no cultivation, saved water at the mean rate of 3.12 
tons per acre during a period of 49 days. 



122 

So cultivating three inches deep as compared with one 
inch has been found to leave the ground 167.4 tons of 
water per acre more moist at the end of the season, and 
this under natural field conditions with corn as the crop. 

187. Flat Cultivation. — When the surface of the 
ground is thrown into ridges, as in hilling potatoes or corn, 
the amount of surface exposed to the air is increased, and 
this, other things being the same, tends to increase the rate 
of evaporation from the surface and diminish the supply of 
moisture for the crop. When three-foot rows are ridged 
to a height of six inches the surface is increased more 
than 5 per cent., and when ridged to the height of eight 
inches, more than 9 per cent. 

188. Deep Tillage to Increase Evaporation. — When 
the ground is stirred to a considerable depth repeatedly 
there is a large and rapid evaporation from the soil stirred, 
and this is one of the chief objects of discing and harrow- 
ing lands that are to be planted early in the spring. The 
ground is cold from the low temperature of winter and 
from the large volume of contained water which requires 
a great amount of heat to warm it. Getting rid of this 
moisture by deep tillage provides a warm and mellow seed- 
bed, well aerated, which also acts as a mulch to conserve 
the deeper water of the soil until a time when it is 
needed. 

1S9. Firniini;- the (xronnd to Control Moisture. — 
Rolling or otherwise lirming land, after it has been tilled, 
may have two distinct objects as regards the control of 
soil- water. These are: 

1. To dry the soil as a whole. 

2. To increase the moisture ot the seed-bed. 

We have shown by two distinct lines of investigation 
conducted in the fields of the Experiment Farm that roll- 
ing tilled land tends to dry the soil, as a whole, the effect 
being measurable at a depth of at least four feet. This 
drying effect is brought about — 

1. By increasing the capillary power of the surface. 

2. By increasing the surface temperature. 

3. By increasing the wind velocity at the surface. 
These three important eff'ects tending to dry the soil may 

be employed to secure the most rapid evaporation when re- 
peated deep tillage and rolling follow each other at short in- 
tervals. Stirring the soil deeply, exposes a large surface 



123 

of moist earth to the air which dries quickly, and if this is 
rolled as soon as dry enough, the soil again becomes wet 
at the expense of the deeper soil moisture, and this is soon 
lost if deep tillage follows. Repetitions of these processes 
ctre an excellent treatment for a seed-bed in too damp cold 

soil. 

When the soil of the seed-bed is too dry for the proper 
germination of seeds, then firming the ground tends to in- 
crease the moisture by bringing it from below to the place 
where it is most needed, and the press-wheels used on va- 
rious forms of drills and planters have this to recommend 
tbem. They concentrate the moisture at the points where 
it is most needed, leaving the remaining portion of the 
field covered with a loose protecting mulch. In the case 
oi broadcast seeding, rolling is generally required, if the 
seed-bed is too dry, and if this rolling is followed, in one 
or two days, with a light harrow to develop a thin mulch, 
it will check the surface evaporation without destroying 
the good capillary connections produced by the rolling. 

190. Puddled Soils.— All soils when completely or 
nearly saturated with moisture become very plastic, and 
when they are worked under these conditions the water and 
air are crowded out of the larger interspaces and the soil 
become much more compact. This is especially true of the 
adhesive clayey soils whose particles, after such treatment, 
become so firmly united as to develop into obstinate clods 
so injurious to good tilth. Great care should always be 
taken not to work soils when they are too .wet. The roller 
should never be used when the soil will adhere to its sur- 

191. Advantages of a Warm Soil.— The advantages of a 
warm soil are several, and may be briefly stated as follows: 

1. Soil ingredients are more soluble in warm than in 
cold water. 

2. Root absorption is more rapid at warm than at cold 
temperatures. 

3. Germination is more rapid at moderately high than at 
low temperatures. 

4. Nitrification takes place most rapidly at about 90*^ F. 
It is a general law with all living beings that their vital 

processes can go on normally only within certain limits of 
temperature, and the range is usually a comparatively 
narrow one. 



124 

In our own case a change of a few degrees above or be- 
low 98° F. in the body, as a whole, produces very serious 
disturbances; and while these ranges are larger with 
plants, yet they are not so wide but that the bounds may 
frequently be crossed. 

192. Best Soil Temi)erature in Certain Cases. — 

Haberlandt found that the germination of wheat, rye, oats 
and flax is best at 77° to 87.8° F., and that corn and pump- 
kins germinate best between 92° and 101° F. He found, 
for example, that when corn germinated in three days at 
a soil temperature of 65.3° F., it required 11 days to ger- 
minate at 51° F., and while oats germinated in two days 
at a temperature of 65.3° F. , 7 days w^ere required when 
the temperature was 41° F. 

Sachs found that tobacco and pumpkin plants wilted 
when the soil temperature fell much below 55<^ F., on ac- 
count of a too slow root absorption. It is found that the 
"mother of i^etre" develops niter at an appreciable rate 
only above a temperature of 54° F., that its maximum 
power is manifested at 98° F. , and that at 113° F. its 
power is less strong than at 59° F. 

193. Control of Soil Temperature. — The tempera- 
ture of soils may be increased in several ways as follows : 

1. By diminishing the water capacity. 

2. By diminishing the water content. 

3. By diminishing the surface evaporation. 125. 

4. By smoothing the surface. 

5. By means of fermenting manures. 

6. By increasing percolation. 

It has been shown, 122 and 125^ that diminishing the 
water in soil and lessening the surface evaporation favors, 
in a marked degree, the production of high soil tempera- 
tures, while the reverse conditions tend in the opposite di- 
rection. 

Smoothing the surface, as in the case of rolling, has a 
very appreciable effect in raising the soil temperature. 
The results observed in a special case are given in Fig. 
48. It will be observed that the air temperature over the 
unrolled ground is higher than it is over the rolled, w^hich 
shows that this soil must be losing heat faster; and since 
both surfaces must have been feceiving the same amounts 
from the sun, it is plain that if the air is warmed more 
over the unrolled ground the soil itself must be warmed less. 



125 



The air receives more heat from the unrolled g-round for 
two reasons. 

1. Its many lumps present a much greater contact sur- 
face. 

2. The lumps being dry become warmer at the surface 
than the more moist rolled soil. 




Fig. Jf8. 

Showing differences of temperature of rolled and unrolled soil and associated air 

temperatures. 

Further than this, the lumps, being in poor connection 
with the soil below, conduct their heat slowly downward, 
while at the same time they shade the, lower soil; and by 
exposing a very large surface to the sky they cool rapidly 
by radiation. 

The measured differences of soil temperature due to this 
cause have been as high as 6.5^ to IC^ F., the lower figure 
having been observed at a depth of three inches and the 
higher at' 1.5 inches. 

The heating effect of fermenting manures in the soil has 
been observed to produce a rise in temperature of nearly 1^ F. 

In the case of well drained soil the percolation of warm 
summer rains often carries rapidly and deeply into the 
soil considerable heat and thus raises the temperature di- 
rectly, and as this water must evaporate more slowly from 
the drained soil, if at all, than from the undrained, it is 
not cooled as much as it might have been had percolation 
not occurred, thus leaving all the water to evaporate in a 
short time. 



126 

194. Effect of Deep and Shallow Culthation on 
Soil Temperature. — Land cultivated three inches deep 
does not warm so rapidly nor cool so quickly as when cul- 
tivated to a less depth. I have found the following differ- 
ences in cornfields cultivated 1.5 and 3 inches deep. 

1st ft. 2nd ft. 3rd ft. 4th ft. 

1.5 inches deep 72.85° R 70.88° F. 68.93° R 65.94°R 

3 inches deep 72.15 70.22 67.80 64.81 

Difference 40 .66 1.13 1.13 

Sudden changes in soil temperature tend to dry the soil 
by expanding the air it contains, causing it to press upon 
the deeper soil-water, forcing it deeper into the ground or 
out into drainage channels. But a deep mulch diminishes 
these sudden changes and hence saves some soil moisture 
in this manner. 



IMPLEMENTS OF TILLAGE 



195. The Plow. — Foremost among the implements of 
tillage unquestionably must be placed the plow. Historic- 
ally, it is probably one of the oldest of farm tools, and 
when viewed from the standpoint of evolution no instru- 
inent has advanced more slowly or has been changed more 
profoundly. It has grown from a natural fork formed by 
the branches of a tree, as depicted on an ancient monu- 
ment in Asia Minor, with the shorter limb simply sharp 
ened and laboriously guided and awkwardly drawn through 
the soil by the longer arm, to our present almost self 
guiding twisted wedge of hardened steel susceptible of an 
extreme polish. 

196. The Work Done by a Plow.— The mechanical 
principles which do or should dictate the construction of a 
plow can be most easily comprehended when a clear notion 
of the work a plow is expected to perform is first in mind. 
Speaking simply of the sod and stubble plows, the first has 
two functions : 

1. A cutting function. 

2. An inverting function. 

The stubble plow has three functions: 

1. A cutting function. 

2. A pulverizing function. 

3. An inverting function. 

With both plows the cutting is required in two planes, 
one vertical and the other horizontal, to separate a furrow- 
slice of the desired width and depth. The inversion of the fur- 
row-slice, required in both cases, necessitates first a lift- 
ing of the slice and then a rolling of it to one side, bottom 
up. The pulverizing of the furrow-slice is most simply 
done by bending the slice upon itself more or less abruptly 
and then dropping it suddenly upon the ground. 



128 




Fig. J,9. 




Fig. 50. 




Fig. 51. 



129 




Fig^ 52. 




Fig. 53. 




Fig. 54, 



130 

197. The Mechanical Principles of Plows. — The 

plows under consideration are sliding three-sided wedges 
having one horizontal plane face, called the sole; one ver- 
tical plane face, called the land-side, and a third twisted 
and oblique face, one portion of which is called the share 
and the other the mold-board. The two lines formed by the 
meeting of the twisted oblique face with the land-side and 
w^ith the sole are cutting edges. This wedge is simply 
shoved through the ground by a force applied to the 
standard through the plow-beam, and is guided in its 
course by a pair of levers in the form of handles. 

A study of Figs. 49 to 54 will show that in these types 
o,f plows, the cutting edges are very oblique to the direc- 
tions in which they move, and that the obliquity is great- 
est in the hreaking type. It will also be seen that the 
strong difference between the elevating and inverting sur- 
faces of mold-boards, in these plows, consists in the steep- 
ness of the iQclined surface and the abruptness of the 
twist in them, these being least abrupt in the breaking 
plow. Fig. 54, and most abrupt in the full stubble. Fig. 49. 

198. Advantage of Obliqne Cutting Edges. — There 
are several conditions which have led to placing the cut- 
ting edges of plows oblique to the direction in which they 
are drawn. 

1. The shin, coulter and share free themselves from 
roots, stubble and grass more perfectly. 

2. The shin, coulter and share require less power to cut 
roots. 

3. The plow enters the ground more easily and runs 
more steadily. 

4. There is less friction of the furrow slice on the in- 
verting surface. 

"When the coulter is placed with its cutting edge in a 
nearly vertical attitude straw and roots tend to double 
around the edge and clog under the beam, increasing the 
draft and tending to draw the plow out of the ground. If 
the coulter is dull and the roots are long and tough, they 
fold over the edge and thus increase the draft by making 
the edge in the soil thicker. When the cutting edge is 
made to incline backward the roots tend to slide upward 
and are severed by a partially draioi7ig cut, and this re- 
quires a less intense power than the straight chisel thrust. 

The obliquity of the share, particularly in the sod plow 



131 

where a large part of its work consists in cutting roots, 
materially lessens the draught by bringing a drawing cut 
upon the roots by forcing them sidewise in its wedging 
action and drawing the cutting edge across them while 
they are under tension. 

When hard spots in the furrow-slice are to be cut through 
the more oblique the share is the greater distance will the 
horses travel before it is cut off, and as the resistance is 
overcome in a longer time less power is required per sec- 
ond. Of course so much work must be done in plowing a 
given length of furrow, but the oblique share tends to de- 
velop an even, steady pull all the time, while the less ob- 
lique form allows the inequalities of the soil to develop an 
irregular draft which is more wasteful. It is, in effect, 
like the triangular sections in a mowing machine, which 
allow the horses to be cutting all the time. 

199. Function of the Land-side — The land-side is 
made necessary by the inequalities of the soil and the tend- 
ency of the horses to vary their course from a straight 
line. When the oblique share is brought against a more 
resisting spot of soil, a root or a small pebble, were it 
not for the land-side the plow would run too far to land 
and the furrow would become crooked. This side pressure 
developed by the share produces friction between the land- 
side and the edge of the furrow and the land-side should, 
therefore, be of such a character as to move most easily 
under this friction. 

200. Tlie Line of Draft. — There is a certain point, A, 
Fig. 55, in the mold-board of the j^low, to which if the 
horses could be attached the plow would "swim free" in 
the soil ; and the attachment of the team to the bridle, B, 
ot the plow should be in such a position that the point of 
attachment, D, of the traces to the harness, shall lie in 
the same plane with A, as represented by the line ABD. 
If the attachment to the bridle is made at C the draft of 
the team will draw the plow more deeply into the ground; 
and should it be at some point below B, or, what would 
amount to the same thing, should the horses be hitched 
shorter, the draft would tend to run the plow out of the 
ground. Not only is it important to adjust the plow so 
that it will "swim free" vertically, but it should likewise 
be adjusted to "swim free" from right to left. When this 



132 



is done, a properly constructed plow will almost hold itself 
and will then move with the least possible draft. 

If the plow requires any considerable power to be ap- 
plied to the handles in guiding it, no matter in what di- 
rection, not only is the work harder for the man, but the 
draft is harder on the team and at the same time the plow 
is wearing out more rapidly. So, too, the man who care- 
lessly holds his plow, allowing it to waver from side to 
side and run shallow and deep, is making not only more 
work for himself and for his team, but is unnecessarily 
wearing out his plow and at the same time producing a 
seed-bed which will necessarily yield a smaller crop. 




Fig. 55. 

201. Draft of the Plow.— The records we have, thus 
far, bearing upon the draft of plows are, in many respects, 
very unsatisfactory, owing partly to inherent difficulties 
in making measurements which represent the actual re- 
sistance of the soil to the plow, partially because of unre- 
liable methods of measurement, and again because the 
varying percentage of water in soil greatly modifies its 
plasticity and its weight. 

Mr. Pusey, in 1840, in England, made some extended 
trials of the draft of plows in soils of different kinds, and 
the figures below show the average results of trials with 
ten plows, the total mean draft being given and also the 
draft in pounds per square inch of a cross-section of the 
furrows plowed: 



133 

No. of Size of Draft. Draft per 

Plows, furrow. sq.in. 

Loamy sand 10 5x9 227 lbs. 5.04 lbs. 

Sandy loam 10 5x9 250 " 5.55 " 

Moorsoil 10 5x9 280 " 6.22 " 

Strongloam 10 5x9 440 " 9.78 " 

Blue clay 10 5x9 661 " 14.69 •' 

Sandy loam (J. C. Morton) 5 6x9 566 " 10.48 " 

Stiff clay loam (N. Y. 1850) 14 7x10 407 " 5.81 " 

Prof. J. W. Sanborn has made extended trials of plows 
recently in Missouri and Utah. The average of all his 
trials, reported in Bulletin No. 2 of Utah Experiment Sta- 
tion, is 5.98 pounds per square inch of furrow turned. If 
we separate these trials historically we get, by leaving 
the clay out of the English trials: 

English trials, 1840, draft per sq. in. 7.41 lbs. 
American trials, 1850, draft per sq. in. 5.81 lbs. 
American trials, 1890, draft per sq. in. 5.98 lbs. 

Both English and American experiments agree in show- 
ing a decrease of power per square inch with increase of 
width of furrow when the depth remains the same; but 
this statement should not be construed as saying that a 
wide furrow can be plowed with less total draft than a 
narrow one. 

The effect of depth on the draft is not so clearly shown 
by the experiments on record, but they appear to indicate 
an increase of power, per square inch, required with in- 
crease of depth. 

202. Effect of the Beam-wheel on the Draft of the 
Plow. — If the wheel under the beam of the plow is so ad- 
justed in height as not to bring the attachment of the horses 
to the plow-bridle above the line of draft there is found a 
material lessening of the draft of the plow with its use. 
The reduction of the draft is occasioned by the more even 
running of the plow, making it unnecessary for the plow- 
man to be alternately pressing down upon the handles or 
raising them, in order to maintain the desired depth of 
furrow. If the wheel is so high as to bring the line of 
draft in the condition represented by the line ACD, Fig. 
55, a part of the power of the team is expended in produ- 
cing pressure downward upon the wheel while the full re- 
sistance of the plow still remains to be overcome. The 
proper adjustment of this wheel is secured when it simply 
rolls on even ground without carrying weight; when in 



134 

this condition it will prevent the plow from entering too 
deeply into the less resisting soils, and will act to force it 
deeper into the harder portions. 

•203. Draft of Sulky Plows, — It is generally claimed 
by plow manufacturers that sulky plows are of lighter 
draft, 'relatively, than the free-swimming types, the claim 
being based upon the assumption that the friction of the 
sole and landside are transferred to the well-oiled axles of 
the wheels and a rolling resistance secured instead of a 
sliding one, which ordinarily, on bare ground, is much 
less. The few records of trials we have seen do not ap- 
pear to show a material difference in the draft. There 
seems to be no good reason, however, why a sulky plow, 
when properly hung and with the line of the draft so ad- 
justed that the power of the horses is not converted into a 
downward pressure upon the wheels, should not lessen the 
draft, and especially in the gang types. If a plow of the 
requisite strength could be made so light that the up- 
ward draft against the furrow- slice were sufficient to take 
the weight entirely from the ground, and if the adjust- 
ment for landing were perfect, there would remain only the 
friction of the furrow-slice itself. In such a case the only 
work left for wheels would be such as has been described 
for the beam- wheel of the walking plow, but such a condi- 
tion appears practically impossible. 

204. Effect of Coulters on the Draft of Plows. —The 
use of the coulter is chiefly confined to sod plowing, and in 
this work it is simply indispensable in securing a proper 
furrow-slice where there is any considerable turf. The 
early English trials, and those of Gould, in New York, in- 
dicate a saving of power by their use; but Professor San- 
born, through his Missouri and Utah experiments, comes to 
the conclusion that they increase the draft from 10 to 15 
per cent, and advises farmers to dispense with them. This 
position is surprising, in the face of g'eneral practice, and 
I believe untenable. When the coulter is very thick, dull 
and set in an improper place or attitude it will necessari- 
ly increase the draft. 

If the coulter is thick and set ahead of the lifting action 
of the plow-point, and especially if it is dull, it offers a 
large resistance by being forced to compress the soil and 
cut the roots at the greatest disadvantage; but if it is so 
placed, in the rear of the point, as to do its cutting and 



135 

side-wedging above the place where the point and share 
are lifting and cutting, the two wedging and cutting bodies 
mutually assist each other; the roots in both cases are then 
severed while under strain and to a greater extent, with a 
drawing cut and, I believe, with an appreciable saving of 
power. So, too, when the wheel coulter is dull and set far 
forward, it becomes necessary to hitch to the plow-bridle 
at so high a point, in order to force the coulter into the 
ground, that there may be loss of power as there may be 
with a beam-wheel ; but when this form of coulter is sharp 
and set well back where the beam of the plow acts with 
leverage to force the coulter through the sod and where the 
cutting occurs under the lifting strain of the point and 
mold-board, there can but be a lessening of draft in tough 
sod. 

205. The Scouring of Plows.— I here are certain soils 
whose texture and composition are such that the most per- 
fect plow surfaces fail to shed them completely. The par- 
ticles of most such soils are extremely minute, 151, and 
often contain much silica. In Fig. 53 is represented a type 
of one of the most successful plows for this class of soils. 
In form it resembles the breaking plow, and the surface of 
the mold-board is very hard and susceptible of a high polish. 
The hard surface in these plows appears to be demanded to 
prevent it from becoming roughened by the scratching of 
hard soil particles; the less abrupt curvature of the mold- 
board diminishes the surface pressure and thus the liability 
to scratching, while the fine polish furnishes the fewest 
and shallowest depressions into which the extremely mi- 
nute particles can be wedged by the pressure. It is a mat- 
ter of great moment, in the care of such plows, that they 
be kept from rusting, because this quickly destroys the 
necessary polish. 

206. Pulverizing Function of Plows— The stubble 
plows are constructed so as to pulverize the soil at the 
time it is being overturned. This action of the plow can 
best be appreciated by taking a thick bunch of paper, like 
the leaves of a book, and bending it abruptly upon itself; 
when this is done it will be observed that the leaves slide 
upon one another, and through a greater distance the more 
abruptly the bending takes place. The steep mold-board 
of the full-stubble plow shown in Fig. 49 has this shearing 



13G 



action upon the soil as one of its chief functions and this 
necessarily increases its draft. 

In selecting plows for the naturally mellow soils where 
pulverizing is unessential, the type represented in Fig. 52 
should be taken, as, other conditions l3eing the same, its 
draft will be lighter. 

207. Care of Plows. — Next in importance to having 
good tools to work with is the keeping of them in proper 
working trim. It is extremely wasteful to purchase good 
tools and convert them into poor ones by lack of care, and 
in no case do these remarks apply with greater force than 
to plows. 

The John Deere Co., in their catalogues, make some re- 
marks regarding the care of plow-shares, and through 
their kindness I am permitted to use some of their illus- 
trations. Figs. 56 and 57 represent a proper and an im- 
proper form of point. A dull point may increase the 




Fig. 56. 

draft of a plow six to eight per cent, and more, besides 
necessitating poorer work. The tendency of wear on the 
point is to change it from the sharp, slightly dipping form 
represented in Fig. 56 to the blunt up-turned form shown 
in Fig. 57. 




Fig. 57. 

The heel of the share, like the poin't, is especially sub- 
ject to wear, and soon comes into an improper shape. 
In case the ground is hard and dry, as is often the case 
during fall plowing, the share-heel requires a set shown 
in Fig. 58, dipping decidedly downward, preventing it 
from lifting out of the ground and tipping the plow to 
land. On the other hand, when the soil is mellow and 



6i 



damp, the heel of the share should be given a more hori- 
zontal attitude, as shown in Fig. 59, to prevent it from 
sucking too deeply into the ground, and necessitating a 




Fi(/. 58. 

steady pressure at the handles toward the land. It should 
be remembered that whenever the plow requires a steady 
pressure at the handles in any direction in guiding it, 
there is a defect somewhere that should be remedied; be- 
cause a pressure of only a few pounds on the long handles, 
working as levers, is transformed into friction, increasing 
the draft on the team and the Tzear on the plow. 

In taking the share to the shop for setting or sharpen- 
ing, the land-side should accompany it, so the blacksmith 
m ay have a guide in giving the proper set to it. 




Fig. 59. 

208. The Subsoil Plow. — One type of this instrument 
is represented in Fig. 60. Its function is nominally to 
loosen the ground to a greater depth than is practicable 
with the ordinary plow, thus securing deeper tillage with- 
out burying the humus-bearing soil too deeply below the 
surface, its use requires great discretion, otherwise more 
harm than good may result from it. Better aeration, bet- 
ter drainage, deeper development of roots and less suffer- 
.ing from drought are advantages claimed for its use. For 
large yields of root crops a deep loose soil is indispensable, 
and one necessity for this is found in the fact that the 
thick roots require so much space which can only be se- 
cured by forcing the soil aside. There is great danger of 
puddling the soil in the use of the subsoil plow, because 



138 



the surface may appear dry enough to work when the sub- 
soil is too wet. 




har- 



Fig. 60. 

209. The Harrow. — As implements of tillage, 
rows are used to secure several quite distinct ends : 

1. To produce a shallow seed-bed. 

2. To dry the soil preparatory to seeding. 

3. To render the surface of the ground more even. 

4. To pulverize the soil and secure a more even texture. 

5. To cover seed. 

6. To destroy young weeds, 

7. To work manure into the surface soil. 

8. To aerate the soil. 

9. To check evaporation by developing a soil-mulch. 

According as one or another of these ends is to be se- 
cured, the character of the harrow should be different. In 
Figs. 61, 62 and 63 are represented three of the strongly 
marked types of harrows, 

210. The Disc Harrow. — This harrow, Fig. 61, is 
distinctly a seed-bed-preparing and soil-drying tool and, 
in its adjustable types, may be made to work to a remark- 
able depth in fall plowing and in corn ground in the 
spring. An immense amount of work can be done with it 
where there is the necessary power to move it, which, al- 
though large when running deep, is really small when 
compared with the amount of soil moved. Its rolling, 
concave, thin discs, when set obliquely, enable it to enter 



139 

the soil and overturn it with less compression and rela- 
tively less friction than almost any other tool. As a first 
tool to loosen the soil and dry it rapidly it does excellent 
work. It is also very effective in pulverizing sod and may 
be used to advantage in covering sowed peas. This is also 
an excellent tool to work in a surface dressing of manure. 




Fig. 61. 

211. The Acme Harrow. — This tool, so far as its ef- 
fects upon the soil are concerned, is like the disc harrow, 
but while it slices the soil and turns it over it does so with 
more compression, more friction and less movement. Like 
the disc harrow it can be used to cut sod, but has a greater 
tendency to drag them out of place. 




Fiy. 62. 



140 

212. The Tooth Harrows. — These tools in their great 
variety of forms, are best adapted to secure the ends 3 to 
9 named in 209. The heavier types are, however, fair 
drying tools, especially on the more mellow soils, and in 
such situations, too, they give a sufficiently deep seed-bed 
for most of the small grains. To kill weeds when just 
emerging from the ground, in potato and corn fields, and 




Fig. 63. 

in developing a light mulch to retard evaporation from the 
soil, there is no tool more effective or rapid in its execu- 
tion than the light, many-toothed harrows. 

213. Cultivators. — We have much to learn yet in re- 
gard to the real objects to be secured by summer tillage 
or cultivation. Three chief objects appear to control pres- 
ent practice; they are: 

1. To kill weeds. 

2. To lessen surface evaporation. 

3. To cover the roots of plants more deeply. 

I believe we shall find, however, that one of the most 
important functions is 

4. To secure better soil aeration. 

When we remember that good aeration, plenty of moist- 
ure, and a warm temperature are among the essentials 
both to soil nitrification and root-growth, and that nature's 
ways of soil aeration are decidedly interfered with by our 
methods of tillage, it seems but natural that some equiva- 
lent should be supplied by our manner of working soil. 

If soil aeration is conducive to its fertility it would appear 
to be rational practice with corn, potatoes and similar 
crops to adopt deep tillage during the early portion of the 
season before the roots have come to occupy the soil, to 
facilitate nitrification, and then to adopt purely surface 



141 

tillage, to check evaporation and kill weeds after the roots 
are well developed. 

214. The Roller. — The firming of land with the roller, 
if used on the soil in the proper condition, has several 
beneficial effects: 

1. It makes the soil warmer, 193. 

2. It increases the capacity of the surface soil for water 
and its capillary power, 189. 

3. In cases of broadcast seeding, the germination of seeds 
is more rapid and more complete on rolled than on unrolled 
ground. 

4. It is maintained by many that larger yields are se- 
cured from rollino; land. 

In cases where the soil is too damp and cold the alter- 
nate use of the harrow and the roller will hasten its drying 
very much. Many farmers advocate the use of the roller 
on lands sowed to small grains after the grain is up es- 
pecially if a drought is threatened, the advantage claimed 
being the formation of a mulch by crushing the surface 
inequalities. It is one of those practices, however, which 
demand careful study and experiment to ascertain to what 
the advantage, if any, is due. 



FARM DRAINAGE. 



(Parts of a paper prepared for the Arkansas Geological Sur- 
vey, 1891.) 

The last twenty years have witnessed a large deve^op- 
ment of the drainage method of land improvement in this 
country, and in no state, perhaps, has this growth been 
greater than in Illinois, where there are many exten- 
sive tracts of very flat lands possessing no sufficiently 
deep water-ways to furnish adequate outlets for drainage 
systems. Notwithstanding these great natural obstacles 
to the improvement of land by drainage, the citizens in 
various sections of the state, by combining their energies, 
have constructed extensive ditches which now serve as 
outlets to the drains they desired to lay. One of these 
systems, in Mason and Tazewell counties, begun in 1883 
and completed in 1886, has a main ditch 17^ miles long, 
with a width of 30 to 60 feet at the top and a depth of 
8 to 11 feet; while leading into this main channel there 
are 5 laterals averaging 30 feet wide at the top and from 
7 to 9 feet deep, the whole system embracing some 70 
miles of open ditch. 

A clearer idea of the character and magnitude of some 
of these drainage systems may be gained from an inspec- 
tion of Fig. 1, where the double lines indicate open ditches 
and the single ones drain tiles, many of which it was 
found necessary to lay very nearly level. This system was 
begun in 1881 and completed in 1884, and its effect upon 
the total yield of grain of all kinds is stated by Prof. 
Baker as follows: 

Total yield of grain in 1881 26,057 bu. 

Total yield of grain in 1882 58,647 bu. 

Total yield of grain in 1883 92.360 bu. 

Total yield of gi ain in 1884 113,660 bu. 

Total yield of grain in 1885 122,160 bu.* 

Total yield of grain in 1886 202,000 bu. 

"^ 400 acres of corn destroyed by a water spout. 



Let these cases serve to indicate the attention which, at 
present, is being given to the improvement of farm lands 
Idv drainage in some sections of this country. 




Fig. I. 

Plan of the drainage of lands of the HI. Agr. Co., Rontoul, Ills. After Prof. I. O. 
Baker. The smal pst squares represent 40 acres; double lines show open ditches; 
single lines drain tile. 

Necessity of drainage. — It should be understood that 
no lands will produce other than swamp vegetation unless 
they are more or less perfectly drained, and this is due to 
the fact that imperfect drainage prevents the biologic 
processes in the soil, which are necessary to cultivated 
crops, from going forward normally because then: 

1. The soil temperature is maintained too low. 

2. There is inadequate soil ventilation. 

3. There is insufficient soil space in which the roots can 
perform their functions. 

Imperfect drainage of cultivated lands works disadvan- 
tageously in two other ways: 

1. By preventing early seeding, thus shortening the 
growing season. 

2. By increasing the labor of tillage and at the same 
time decreasing the time in which it can be performed. 

So thoroughly does the lack of drainage insure the diffi- 
culties here enumerated and so effectively does perfect 



144 

drainage avert them that it becomes of prime importance 
to realize the full significance of each. 
Iiiiportance of the ris^ht soil temperature. — It is a 

general law with all types of life that their vital processes 
can go on normally only within certain narrow limits of 
temperature. In our own case deviation of the general 
temperature of the body a few degrees either side of 98. S'^ 
F. results in the most serious disturbances. While vege- 
tal life is less sensitive, as a rule, to small changes of 
temperature than is animal life, yet no physiological law 
is more surely established than that a fluctuation of tem- 
perature above or below that normal to a given plant im- 
pedes its growth. Haberlandt found, for example, that the 
germination of wheat, rye, oats, and flax goes forward 
most rapidly at from 77^ to 87.8'^ F., and that corn 
and pumpkins germinate best between 92° and 101° F. He 
found that when corn germinated in three days at a tem- 
perature of 65.3° F., it required 11 days to germinate 
under a temperature of 51° F., and that when oats ger- 
minated in two days at a temperature of 65.3° F. , it re- 
quired seven days when the temperature fell to 41° F. 

It has been shown that the "mother of petre" or nitric fer- 
ment {Micoderma aceti) ceases to produce nitric acid from 
humus at a temperature of 41° F. ; that its action only be- 
comes appreciable at 59° F., that it is most vigorous at 
98° F., accomplishing in a short time results for which, 
under other conditions, months would be required ; but at 
113° F. the activity again falls below that at 59° F. 

Sachs found that, with plenty of moisture in the soil, 
tobacco and puaipkin plants wilted at night, because of too 
slow absorption by the roots, when the temperature fell 
much below 55° F. 

The advantages of warm soil temperatures are not wholly 
due to their direct physiological effects upon the life pro- 
cesses going on there, so essential to large crops, but some 
of them are purely physical and chemical, but nevertheless 
indirectly important and the several advantages of a warm 
soil may be briefly stated as follows: 

1. The soil ingredients of plant food are more soluble 
in the soil-water thus enabling it to carry more food to the 
roots. 

2. The chemical reactions are more rapid in the produc- 
tion of soluble minerals for the water to take up. 



D45 



3. The rate of diffusion of the newly forming substances 
is more rapid and this hastens the chemical action. 

4. The rate of root absorption is greater, making a more 
rapid growth possible. 

5. The rate of germination is more rapid and more vig- 
orous, thus securing an earlier start and stronger plants. 

6. The rate of nitrification is more rapid, thus supply- 
ing a large quantity of an important plant food. 

Influence of drainage on soil temperatures. — It 
is a fact of common experience that a wet soil has a lower 
temperature than the same soil similarly conditioned but 
dryer. The following table gives a series of temperature 
records taken by the writer the last of April, 1884, at 
River Falls, Wis., two inches below the surface of the 
soil on undrained and on well drained land. 



Date. 



Apr. 24 
Apr. 25. 
Apr. 26 
Apr. 27. 

Apr. 28. 

Apr. 29. 



Time. 



3:30 to 4 P. M 
3 to 3:30 P. M 
1:30 to 2 P. 31 
l:30to2P. M 

7 to 8:30 A. M 

4:30 to 5 A. M 



Condition of the 
weather. 



Cloudy with brisk 
east wind . 

Cloudy with brisk 
east wind . 

Clf^uiy, rain all 
the forenoon . . . 

Cloudy and sun- 
.«hine; wind 
S. W., brisk 

Cloudy and sun- 
shine; wind 
N. W., brisk 

Clear; gf round a 
little froz^^n 



Temp 
of air. 



60° F. 
64° F. 
45° F. 



53° F. 



45° F. 
34° F. 



Temp, of 

drained 

soil. 



66.5= 

7G° 

50° 

55° 

47° 
35° 



Temp, of 

undrained 

soil. 



54° 
58° 
44° 

50.75= 

44.5° 
34 5° 



Diff. 



12 5° 
12° 
6° 

4.25* 

2.5° 
.5° 



It should be noted in connection with this table, that 
the differences of temperature which were observed in favor 
of the well drained soil occurred under conditions of cloudy 
and rainy weather when these ditt'erences should, naturally, 
be the smallest. It will also be seen that a difference per- 
sisted through the entire night, and that the temperature 
of the undrained soil did not reach the point at which the 
nitre gems produce appreciable quantities of nitric acid. 

To understand why the presence of water in the soil re- 
tards the rise of its temperature two physical principles 
require consideration : 

1. A larger number of heat units must enter a given 
weight of water to raise its temperature one degree than 



140 

is required to enter an equal weight of any soil to produce 
an equal change of temperature in it, the relative changes, 
in certain cases, being as stated below: 

100 heat units will raise 100 lbs. of water at 32° F. to 33° F. 

100 heat units will raise 100 lbs. of dry sand at 32° F. to 41.92° F. 

100 heat units will raise 100 lbs. of dry clay at 32° F. to 39.28° F. 

It is evident, from these figures, that undrained soils 
must warm more slowly under the same sunshine than cor- 
responding well drained soils will. -js- * * * * ^ 

2. To evaporate one pound of water, under mean atmos- 
pheric pressure without change of temperature, requires 
the expenditure of 9(50. C heat units and in this fact is to be 
souo'ht the chief cause of low temperature observed in wet 
soils. If two similar thermometers are taken and the bulb 
of one covered with a film of water and then both swung 
at ai'ms length to and fro in a drying atmosphere the ther- 
mometer with the wetted bulb will be found to read several 
degrees below its companion, if the reading is taken before 
all the water has been evaporated, and the difference in 
temperature may be found, with dry, warm air, greater 
than 30*^ F. ; thus demonstrating the cooling effect of 
evaporating water. 

When a pound of water is evaporated from a cubic foot 
of soil it carries with it heat enough to lower its mean 
temperature, if saturated sand, 32.8*^ F., and if saturated 
clay loam 28.8'^.; and in this connection it should be 
abundantly evident that draining land of the water which 
it cannot hold by capillary power will permit it to attain 
a higher temperature. 

There is still another manner in which thorough drainage 
tends to permit higher soil temperatures to exist. It is 
this: As the season advances and the surface foot of soil 
becomes dry, its upper portion especially becomes very hot, 
often above 100^ F., and in such cases, when heavy rains 
fall upon porous, well drained soil to such an extent that 
percolation takes place, the warmth of the surface soil is 
imparted to the percolating water and carried by it deeply 
into the ground thus increasing the temperature of the soil 
which is occupied by the deeper roots : but in undrained 
soil this percolation is always less extended and less fre- 
quent. 



147 

Importance of soil yentilatioii. — The necessity for a 
considerable circulation of air in soils maintaining growing 
vegetation is now generally recognized and the demands 
for it are three-fold: 

1. To supply free oxygen to be consumed in the soil. 

a. In the respiration of germinating seeds. 

b. In the respiration of growing roots. 

c. In the respiration of nitric acid germs. 

d. In the respiration of free-nitrogen-fixing germs. 

e. In the respiration of manure-fermenting germs. 

f. In simple chemical oxidations. 

2. To supply free nitrogen to be consumed and fixed for 
the use of plants by free-nitrogen -fixing germs. 

3. To remove carbon dioxide, liberated in the soil, thus 
preventing excessive dilution of the oxygen and nitrogen. 

It has been abundantly demonstrated that when free 
oxygen is completely excluded from seeds, placed under 
otherwise normal conditions for germination, growth does 
not take place; if the germination is allowed to commence 
and then the oxygen is excluded growth ceases. Germi- 
nation will, indeed, take place in an atmosphere very poor 
in oxygen but it has been shown that when the percentage 
is reduced to 3V of the normal amount the rate of growth 
is retarded and sickly plants are likely to result. 

Practical experience teaches that when a soil, bearing 
other than swamp vegetation, is flooded with water or even 
if it is kept long in a fully saturated condition the plants 
soon sicken and die and this too when they are in full leaf 
and abundantly supplied with nourishment, sunshine and 
warmth. The difficulty is the lack of root breathing; oxy- 
gen in sufficient quantity to maintain life cannot reach 
them and actual sutfocation occurs. It may be urged that 
this explanation of the death of plants under these condi- 
tions is disproved by the floating gardens of the Chinese 
which consist of basket work made strong enough to carry 
a layer of soil in which the crops grow with their roots 
constantly immersed in the water. The two cases, how- 
ever are far from being parallel. In the cases of water 
culture the free water is subject to strong convection and 
other currents which bring the oxygen absorbed by the 
water constantly to the roots of the plants; but in the soil 
with less than half the volume of water per cubic foot of space 
convection currents are wholly prevented, while simple dif- 



148 

fusion from the atmosphere downward into the soil is nec- 
essarily much slower than it is in free water. 

The nitrification of soils, so essential to their fertility, 
and effected, as w^e have seen, by living germs, requires 
an ample supply of oxygen; so large is this demand that, 
when salt petre farming was practiced in parts of Europe 
the soil was kept well aerated by frequent stirring and by 
the introduction of gratings to increase the air spaces and 
promote better ventilation of the niter beds. 

While we have as yet less positive knowledge in regard 
to the respiratory needs of the free-nitrogen-fixing germs, 
which have been shown to inhabit tubercles on the roots of 
liguminous and other plants, and whose agricultural im- 
portance is now coming rapidly into recognition, there is 
no reason to doubt the beneficial effects of a well aerated 
soil upon them. They ■ must certainly be supplied with 
atmospheric nitrogen which it is their function to fix and 
turn over to the hosts upon which they live. 

In regard to the manure-fermenting germs, we have suf- 
ficient evidence of the need of good ventilation in the strong 
heating of the well aerated heaps of horse-manure, when 
contrasted with the smaller amount of fermentation which 
takes place in the close cow dung free from litter. 

There are many purely chemical reactions essential to 
soil production and soil fertility which demand a certain 
measure of free oxygen for their continuance. Then again, 
not only must oxygen and nitrogen be introduced into fer- 
tile soils, but the carbon-dioxide liberated by the processes 
of fermentation and by the decomposition of bicarbonates 
brought up by capillary soil waters, must be disposed of in 
order that it may not prevent the entrance of oxygen and 
nitrogen or make them too dilute for respiratory purposes. 

Influence of drainage on soil ventilation. — Ample 
drainage facilitates the aeration of soils in three chief ways : 

1. By drawing off' the water from all non-capillary spaces 
in the soil, thus not only permitting but forcing, by down 
ward suction, the air to take its place. 

2. By both permitting and inducing earth-worms and 
other burrowing animals to extend their channels more 
deeply into the ground. 

3. By allowing the roots of plants to grow more deeply 
where, after decaying, they leave passages into which the 
air may penetrate. 



149 

All soils, when not saturated with water, are subject to 
a small but irregular type of breathing clue to expansions 
and contractions of the soil-air resulting from changes of 
atmospheric pressure and of soil temperature. The 
amounts of air put out of and taken into the soil by the 
maximum daily temperature changes can not much exceed 
22 cu. in. to the square foot of soil surface and probably 
average less than one half of this during the growing sea- 
son, and yet these effects are larger than those due to 
barometric changes. It is evident, therefore, that the chief 
renovation of soil-air must result from the process of dif- 
fusion which must necessarily be slow under the best of 
conditions. I have found by experiments conducted in the 
field that saturated clay and black marsh soils are practic- 
ally impervious to air under a suction of one pound to the 
square inch; it is evident, therefore, that the diffusion of 
air must also be very slight under these conditions. But 
well drained soils very soon cease to be saturated and a 
large amount of space only occupied by air and roots is 
developed. 

•^ — JA Ai " " .. 

How drainage increases root-room and the amonnt 
of available water. — That draining land to a depth of 
three, four or five feet increases the amount of stored water 
available to crops appears like a parodoxical statement and 
yet it is strictly true. The depth of the root zone is lim- 
ited by the downward extent of ample soil ventilation and 
this, in turn, by the distance of saturated soil below the 
surface. When standing water exists at three feet or less 
below the surface the roots of cultivated plants can only 
extend to a depth of sixteen to twenty inches: and when 
the root zone is so shallow the water, under the combined 
action of the dense net- work of roots and surface evapora- 
tion, is withdrawn more rapidly, during dry weather, than 
capillary action can supply it from below.*^ The result of 
these conditions is the j^roduction of a very dry soil into 
which the capillary movement is extremely slow even when 
standing water is only twelve to eighteen inches below. 

When the soil is adequately drained the roots are ex- 
tended deeply into it before the moisture is so thoroughly 
exhausted and hence a larger amount of stored water be- 
comes available, a much larger root-pasturage is secured and 



150 

a more equable activity is maintained by all the roots. 
But the most important gain as regards moisture, lies in 
the fact that the surface soil, is maintained more moist 
thus permitting soil nitrification to continue and at the 
same time leaving moisture enough about the surface roots 
to make the developing fertility available to the crop. 
That is, under these conditions the deeper roots, pumping 
water from far below the surface relieve the more super- 
ficial ones from drawing as much and hence the upper foot 
remains more moist than it would had the soil been un- 
drained. first because the rate at which water is 
removed from it is slower and second because the rate of 
capillary flow into it from below is more rapid on account 
of its not becoming excessively dry. 

Lands likely to be benefited by drainage. — It is a 
fortunate coincidence that most of the lands which are 
likelv to be improved by artificial draiaage become, when 
reclaimed in this way, the richest of cultivated fields; 
they are so first, because they often receive, through both 
surface and underdraihage, much of the fertility developed 
on surrounding areas, and second, because they are then 
usually provided with what is much more important, a larger 
water supply automatically controlled. 

The majority of lands, when large areas are considered, 
are sufficiently drained by natural processes and many in- 
indeed are overdrained. Most of those which may be ma- 
terially improved by artificial drainage fall under the fol- 
lowing; heads: 

1. AH lands where standing soil water is usually found, 
at seeding time, not more than four feet below the surface. 

2. All very flat lands underlaid, at a depth less than 
four to six feet, with a stratum of highly impervious clay 
or rock. 

3. Ponds and sloughs generally. 

4. Springy hillsides and cold springy lands of all kinds. 
It is a fact well proven by practical experience that 

many low lands, which require draining in order to bring 
them under cultivation, and lying adjacent to higher areas, 
become, when so treated, the most productive lands of the 
locality, and while there are several conditions which 
tend to render them so, the chief one is the water supply 
naturally provided by the upward tendency of it under the 
low lands coming from the supply of stored water in the 



151 



soil of the surrounding highei' ground. This is because 
the water level being higher, tends to lift by hydrostatic 
pressure, some water up into the soil of the lower fields, 
that is to say, the lower fields are supplied from below 
with water which falls upon the higher ground. 






- — :^J^ ^iV"'*^;':i^f'^| ±': ir. ' V_V: ' <^ - ^/t^^:JX''-^:x^^^ 










'm^^^^^A 



Fig. 2. 

Stowiug the geologic structure favorable to natural subirrigation. 

Not all low lands adjacent to high areas are equally sub- 
ject to the natural subirrigation referred to, for differences 
in the structure of the soil necessarily modify the move- 
ment of the rain which has entered the ground. The 
structure best suited to the storing of water in the high 
lands and the giving of it out gradually to the adjacent 
lower areas is represented in Fig. 2 where the surface of 
the lower areas is covered to a depth of three to four feet 
with clay soil and subsoil; on the highland this mantle 
passes, by degrees, through a porous, sandy and gravelly 
clay into a sand and gravel or pure sand of considerable 
depth into which the water percolates rapidly, and out of 
which it flows laterally with comparative ease toward and 
below the adjacent lower areas. This type of geological 
structure is very common in many parts of Wisconsin 
and other sections of the United States which are heavily 
mantled with the deposits of the glacial epoch. The ter- 
minal morains of this and other states are water reservoirs 
of great extent and capacity into which the rains sink at 
once and are there stored under conditions of the least 
possible loss by surface evaporation, to be given out grad- 
ually in restricted but innumerable areas. Heavy rains, 
which in other sections are lost to agriculture in destruc- 
tive floods, are here safely and economically stored and it 
is these very many naturally subirrigated tracts to which 



152 



I wish to call attention as being so promising for the pur- 
poses of market gardening and other types of intensive 
farming. 

Best depth for drains. — From what has been said in 
regard to the importance of root- room it is evident that, 
where it is possible, tile drains should be placed at a depth 
of three to four feet. Inequalities of the surface and the 
great increase in cost of digging ditches more than four 
feet deep often make it necessary, in order to maintain the 
proper grade, to place some portions of the drain nearer 
to the surface than three feet, but jDcrmanency demands 
that the tile should never be laid near enough the surface 
to be destroyed by freeziDg. Indeed the cases should be 
very rare where the tile are placed nearer the surface than 
2.5 feet. It is often found necessary in draining flat land 
to lay the main drains deeper than four feet in order to 
secure a sufficient fall for the laterals. 

Best distance between drains. — The deeper the drains 
can be laid and the more open and porous the soil the 
greater may be the distance between the two lines. 




Fig. 3. 

Showing how the distaLce between drains affects the depth of drainage. With 
drains at A and C the surface of the Wbter will be higher at LJ; but with drains at 
A, D and (J the surface ot the water will be more nearly that of the lines A, E, D, F, C 

In many prairie soils and in light loams, where the tile 
are laid at a depth of 3.5 feet, very excellent drainage is 
secured with the lines placed 100 feet apart, but in the 
heavy and stiffer clays and especially where the summer 
rains are frequent and heavy 75. 50 and even 40 feet have 
sometimes been found necessary. It should be said, how- 
ever, that larger distances than 100 feet apart are fre- 
quently adopted, sometimes as great even as 220 feet, and 
150 feet is a distance often used for general farm drainage 
in Illinois. If the drains are too far apart, and especially if 



153 



they are shallow, there is inadequate drainage midway be- 
tween the lines. Why this must be so will be readily seen 
from an inspection of Fig. 3, for the closer the soil and the 
more distant the drains, the nearer the surface will the 
undrained soil approach and the longer will that which is 
affected remain too wet. 







Fig. U. 

ShowiDg the surface of ground-water between tile drains 48 hours after a 
rain-tall of .87 inch. 

Since writing the above the actual surface of the ground- 
water 48 hours after a rain fall of .87 inches in a tile- 
drained field at the Experiment Station which is shown in 
Fig. 4, has been observed by the writer. In this instance 
the drains are 33 ft. apart and lie in a medium grained 
sand overlaid with clay. The height of water above the 
tops of the tile, midway between the drains, varied at this 
time, between 4 and 12 inches, and the mean rate of rise 
was one foot in about 25 ft. ; that is to say, in soil of this 
character, when the drains are placed 50 ft. apart the 
ground- water will stand midway between them 48 hours 
after such a rain, 1 ft. nearer the surface than the drains 
themselves, and if 100 ft. apart, then 2 ft. nearer the sur- 
face. It is evident therefore, that the deeper the drains 
are placed, the further apart they may be and that if tiles 
are placed 100 ft. apart and 3 ft. deep, the land midway 
between the lines would not be sufficiently drained because 
then standing water might reach within 12 in. of the sur- 
face in parts of the field. 

It should not be understood that Fig. 4 repi^esents the 
permanent slope of the surface of standing water in the 
field in question, for that surface is constantly changing, 
and in Fig. 5 is shown just how the surface did change be- 
tween the dates given in the cut, the three broken*^ lines 



154 



representing the levels of the water on three different 
dates. 




Fig. 5. 

Showing change in the level of water between tile drains. 

The grade of drains.— Securing a sufficient and 
proper fall or grade for lines of tile is one of the most im- 
portant problems of practical drainage. As a general rule 
it is desirable to secure all the fall that is possible, and 
this is especially true for all flat and large areas. The 
greater the fall per 100 feet the more rapidly will the 
water be removed, the less danger will there be of the tile 
becoming clogged with silt and the smaller may be the 
tile used. A fall of two inches in 100 feet, one foot in 
600 feet or 36 rods, has been found very satisfactory where 
the tile have been carefully laid; it is often necessary, if 
draining is done at all, to adopt a less steep grade than 
this, but higher grades are much safer and more effective 
and should be secured where circumstances will permit. 

When a particular grade has been decided upon it is a 
matter of the greatest importance, in the laying of the 
tile, to see that each and every piece is immovably placed 
exactly on the grade line. If careless laying of the tile is 
tolerated, which results in one section being placed above 
the grade line while another falls below it, sediment will 
tend to collect in the sags, and if the fall is slight, the 
tile small, and the deviation from the grade line nearly 
equal to the internal diameter of the tile, ultimate clog- 
ging is almost inevitable. It is often absolutely necessary 
to lay two or more sections of a line of tile on different 
grades, and in such cases it is always best to have the 
water pass from a less steep to a steeper grade, when this 



155 



is possible, but when this is impracticable a change to a 
larger size of tile on the less steep grade will help to pre- 
vent clogging. 

The outlet of drains. — The securing of a proper outlet 
for a drain is of scarcely less importance than laying the 
tile true to grade. In any case where the mouth of the 
drain is under stagnant water there is a tendency for the 
mouth to become clogged and thus render the whole system 
ineffective. 

Fig. 6 represents a good and a defective outlet. In very 
fiat sections like that represented in Fig. 1, proper outlets 
can only be secured by the construction of deep open 
ditches. Where lateral drains are connected with main 
lines, junction tile, represented in Fig. 6, should be used, 
and it is important that the angle should be acute up- 
stream, otherwise the velocity of the water in the main is 
checked, and there is a tendency to clo^ both the main and 
the lateral. 




il 



\D 




Fig. 6. 

Showing proper and improper outlets of draias. A, proper outlet; B. improper 
outlet; C, proper juQcLioQ ■)? lateral wita mala draio; D, improper jnaction. 

Obstructions to drains. — Where elm, willow, larch or 
other water-loving trees are allowed to grow nearer than 
75 feet to a drain they are very certain sooner or later to 
extend their roots into the tile through the joints and 
there branch out into a vast network entirely filling the 
tile where, by retaining the silt brought by the water, 
they effectually close up the drain. * * * ^ 

Main drains and laterals. — In draining any consider- 
able number of acres of land, one or more main drains with 
systems of laterals leading into them are required. To 
illustrate the manner of distributing and joining, I have 
selected an actual case which represents a farm of 80 
acres in Northern Illinois which has been drained under 



156 



the supervision of Mr. C. G. Elliott, C. E., who describes 
the soil as a rich black loam, approaching black muck in 
the ponds and flats, underlaid with a yellow clay sub-soil 
at a depth of '2.b feet from the surface. The mains, Fig. 
7, have a grade of two inches per 100 feet and the laterals 
not less than this and sometimes more. In draining this 
land the object was to fit it for growing corn, grass and 
grain in all seasons. 




Fi(/. 7. 

Showing: the drainage system on an 80 acre farm in Northern Illinois after C. G. 
Elliot, C E. Double lines repiesent mains; singles lines, laterals, and the numbers 
express the length ol dr-einf and the size of tile used. 

It will be seen that the lateral drains are, where nearest, 
150 feet apart; and it should be understood that this sys- 
tem is not intended to provide perfect drainage but rather, 
as good as would pay a fair interest on the investment 
under the returns of general farming. 

This figure may also serve to show how the sizes of tile 
are selected and placed with reference to the amount of 
work they are called upon to do. 



THE CONSTRUCTION AND VENTILATION OF FARM 

BUILDINGS. 



(A lecture prepared under the direction of the United States De- 
partment of Agriculture, Office of Experiment Stations, for the 
exhibit at the World's Columbian Exposition, 1893.) 

In discussing the construction and ventilation of farm 
buildings, since there are in fact such great variations in 
the details even where the main objects to be attained are 
the same, it will conduce to clearness and brevity if atten- 
tion be given chiefly to those fundemental principles which 
should govern the construction of all buildings of this 
class, whatever may be the specific use for wliich they are 
intended. 

FUNDAJIENTAL PRINCIPLES. 

The construction of a shelter should in no way ser- 
iously interfere with the bodily functions of the animals 
housed; a shelter should provide ample ventilation, suffi- 
cient light, and the required degree of warmth, cleanliness, 
and comfort. The construction and the arrangement of 
parts should be such as to reduce the labor of caring for the 
animals to the smallest amount consistent with the largest 
net profit and should require the smallest first net cost and 
the smallest maintenance expense compatible with the 
necessary accommodations. 

THE NEED OF THOROUGH VENTILATION. 

Now that farmers are coming lo appreciate the advan- 
tages of warm shelters for stock and are endeavoring to 
provide tight, well built barns, the importance of under - 
standing the need of ample ventilation and the best methods 
of insuring it becomes very urgent. 

The oxygen breathed by ourselves and by our domestic 
animals is procured so unconsciously and so inevitably 



158 

under ordinary conditions that we rarely realize the im 
portant part which it plays in the physiological processes 
or the large quantity of it which is daily required. 

Let me endeavor to impress upon your minds a notion 
of the quantity of oxygen used daily by some of our do- 
mestic animals. Experiments conducted for the purpose 
have indicated that steers consume oxygen at the rate of 
13.24 lbs. per every 1,000 lbs. of weight per day: horses 
13.5 lbs. and sheep 11.75 lbs. Now air is a very light 
substance and only about one-fifth of it is oxygen : neither 
can all of the oxygen contained in the air be removed from it 
by the lungs when once breathed, and hence it has been 
found that to obtain the 13.21 lbs. of oxygen needed in 24 
hours, the 1,000 lb. steer must breathe 2,513 cubic feet of 
air; the horse 2.552 cubic feet, and the sheep 2.222 cubic 
feet, and these are the volumes of pure air these animals 
must take into and put out of their lungs for each 1.000 
lbs. of weight, daily. 

Now air once breathed contains less than the normal 
proportion of oxygen and is really unfit for the mainte- 
nance of animal life unless largely diluted with that which 
is pure. This may be demonstrated before your eyes in a 
verv simple manner. Let me lower this lighted taper into 
the" jar before vou. It burns brightly as it did before; but 
now let me replace the air with that from my lungs. On 
lowering the taper into it it is at once extinguished. Re- 
filling the jar with fresh air the taper again burns 
brio-htlv in it, but on breathing into it the taper is again 
extinguished, showing that it was by no accident that it 
went out before. 

Neither man nor his domicstic animals can survive in 
an atmosphere in which a candle will not burn; it follows, 
therefore, from this experiment that air once breathed 
should be rapidly removed and replaced by that which is 
fresh even to permit life to exist. 

Twenty cows should not be housed in a space much 
smaller than 28x33 sq. ft. and 8 ft. ceilings. These cows 
would breathe the volume of air represented by this room 
in 3.3 hours: but, as the air once breathed is thrown di- 
rectly back into the room so as to dilute the oxygen of the 
unbreathed air, it follows that in order that the cows may 
have air containing not more than 3.3. per cent, of that 
once breathed it must be changed at the rate of 8.8 times 



159 

each hour. This would be accomplished Vjy a ventilating 
shaft 2x2 ft. in section through which the air moved at 
the rate of three miles per hour. Forty cows would require 
two such ventilators, 60 cows three, 80 cows four, and 100 
cows five. These statements assume that the cows average 
1,000 lbs. in weight. If they do average 1,200 lbs. or if 
the space in which they are housed is smaller than that 
assumed, then the rate at which the air is changed should 
be relatively increased. 

It should always be born in mind, too. that where ani- 
mals are doing a relatively large amount of digestion work, 
as in the case when animals are being fattened or when cows 
are being fed high for milk production, much larger 
amounts of oxygen are required than when simply a main- 
tenance ration is being fed. 

It has been found, with man, for example, that when 
fasting and at rest only 1,627 cubic inches of oxygen was 
consumed per hour, but while at rest during digestion, 
that 2,300 cubic inches were consumed, or more than 57 per 
cent, more oxygen. From analogy we should expect to 
find the same relation to exist in the case of our domestic 
animals ; and from this it follows that with high feeding- 
should always be associated the best of ventilation. No 
engineer thinks of increasing the output of his engine by 
simply adding coal ; he at the same time opens wider the 
draught that more oxygen may also be supplied, knowing 
well that if he does not increase the supply of oxygen his 
fuel is wasted as smoke. Now, just as in this case, high 
feeding with inadequate ventilation must of necessity re- 
sult in loss of feed passed from the body unused or in a 
diminished desire or capacity to eat on the part of the 
animals so treated. 

In a preliminary experiment on the influence of ventila- 
tion on milk production conducted at the Wisconsin Agri- 
cultural Experiment Station, it was found that, with 20 
cows the milk production was 3.57 per cent, less where 
the ventilatino- shaft had a cross section of 12x16 inches 
than when the ventilation was ample, 

THE NEED OF THE RIGHT TEMPERATURE. 

All animals are so con.stituted that the bodily functions 
can go on normally only within certain narrow limits of 
temperature and their nervous organization is such that 



160 

they can increase or decrease the heat produced in the 
body within certain limits; but it must be remembered 
that work done in either one of these directions is at the 
expense of food eaten and of the amount of useful product 
sought. 

It has been found with man, for example, that when fast- 
ing and at rest and exposed to a temperature of 90" F. he 
consumed 1,465 cu. in. of oxygen per honr but Ainder the same 
conditions except that of being exposed to a temperature 
of 59^ F. the consumption of oxygen was 1,627 cu. in. or 
13.3 per cent, greater, and this increase in the consump- 
tion of oxygen was associated with a corresponding in- 
crease in the amount of carbon dioxide given off, which 
means, of course, an increase in the waste of food eaten. 

Now the same must be true of our domestic animals. 
If they are sheltered in quarters in which the heat gen- 
erated by the necessary vital processes does not suffice to 
hold the temperature of the body up to the proper limit 
then food eaten and oxygen breathed are both converted 
into waste products for the sole purpose of securing the 
necessary temperature and this can in no direct way con- 
tribute to the production of milk, flesh, wool or eggs. So, 
too if the necessary vital processes produce heat faster 
than the surrounding temperature will allow it to escape 
from the body, the system is forced to make a direct effort 
to increase the perspiration for the purpose of carrying 
away the surplus heat, and this, too, means a loss of feed 
and a reduced capacity of the animals in useful directions. 

THE CONSTRUCTION OF STOCK BARNS TO INSURE PROPER 

VENTILATION. 

Let us now consider the construction of a dairy barn in 
which special attention has been paid to the proper ven- 
tilation and warmth of the stable for the cows. In this 
view, Fio;. 1, is shown the exterior of the barn with a 
dairy house attached. This barn accommodates 98 cows 
and 10 horses, and has been in use for four years. Fig. 
2 is a perspective drawing showing the plan of the base- 
ment where the cows are arranged in two circular rows 
facing one another about a central silo having a capacity 
of over 300 tons. In this barn, as shown by the diagram, 
every space between the studs of the silo wall constitutes 



161 




Fig.l. 



mjjW 




Fiy. 2. 



162 

a ventilating flue 34 feet long, and the air is drawn into 
these flues at the level of the stable floor instead of at the 
ceiling. The latter is the usual method of ventilating a 
stable where any effort is made in this direction at all. 
By this faulty method not only the warmest but the purest 
air is removed while the coldest and most impure air is 
allowed to stao-nate where the animals must breathe it not 
only while feeding with their heads near the floor, but also 
while lying down. By the better method, however, Fig. 2, 
the air which has been warmed by the bodies of the ani- 
mals and is relatively pure rises to the ceiling where it 
remains until it cools and falls to the floor to be drawn 
off with the foul air which is breathed directly downward 
by the animals and where it tends itself to settle because 
it is heavier than pure air of considerably higher tempera- 
ture. 

The combined capacity of these ventilating flues aggre- 
gates more than 25 sq. ft. (Fig. 3), and they are secured, 
it should be noted, without using either additional space 
in the barn or one foot of extra lumber. The flow of air 
through them, too, has been found by direct measurement 
to exceed 3.5 miles per hour when there was only a mod- 
erate wind and winter temperature outside. This strong 
ventilation is due not simply to the long flues, but also to 
the fact that they are at the center of the building where 
the air in them is not chilled by the outside low tempera- 
ture. An effort has been made in the construction of 
some barns to carry the air up along the outer wall and 
between the rafters at the roof, but such flues must always 
be less effective in the winter season because the air is so 
much chilled by the cold outer wall, 

A method of ventilating sheep barns which has been 
found fairly effective, is illustrated in this photograph, 
Fig, 4, where the w^hite columns are ventilating flues made 
of wood extending from near the floor up through the roof 
near one side of the stable. Had these been extended up 
through the ridge of the I'oof they would have been much 
more effective, not only because of their greater length but 
also because of the greater suction developed by the wind 
in blowing across their tops. 

VENTILATION OF A WARM BARN. 

Where an effort is made to construct a warm shelter for 
animals, provision should always be made for the entrance 



IG3 




ti</. 'J. 




Fig. ^. 



164 

of fresh air from without as well as for the exit of the 
foul air within, because unless there is ample provision for 
air to enter from without there can be only inadequate 
ventilation within, for air can leave a compartment no 
faster than it enters it. 

In this round barn, Fig. 2, entrance for air is provided 
through a series of auger holes throug-h the siding just 
above the sill. The inside sheeting not shown in the 
plan, on one side of the studding, and the siding on the 
other constitute cold air flues through which the fresh air 
rises and enters the stable at the ceiling as indicated by 
these arrows. By this arrangement the cold air is min- 
gled with the warmest air of the stable and has the chill 
taken from it before it comes in contact with the cows be- 
low. Of course it would not do to have the auger holes 
through the siding at the level of the ceiling, for in this 
case the warm air would always leave the stable on the lee- 
ward side and cold air would blow in on the windward 
side. 

In my judgment the bad effects which have been attrib- 
uted to basement barns for sheep on account of "damp- 
ness" are in reality usually due to imperfect ventilation. 
Any well drained basement or cellar may be as dry as any 
other compartment of the same structure if it is only 
properly ventilated. Since the basements of barns have 
usually tight outside walls and since there is rarely any 
provision in them for the entrance of fresh air from with- 
out, they are often very poorly ventilated and rendered 
damp by the moisture thrown into the room from the lungs 
and bodies of the animals housed. Now sheep suffer less 
in a dry, cold, pure air than they do in one which is foul, 
but the normal temperature of a sheep is high and 
they have a thick coat of wool for the express purpose of 
economically maintaining it, and a fairly warm stable with 
ample pure air it would seem is what is needed for eco- 
nomical maintenance. 

ECONOMY IN FIRST COST. 

Let us look now to the construction of buildings with a 
view to economy of first cost. Here is the floor plan. Fig. 
5, of what has been regarded as one of the best planned 
horse barns in Ontario. It is convenient and commodious 



165 



in its appointments but expensive on account of the rela- 
tive dimensions adopted in its construction. It is 150 ft. 
10 in. long and 30 ft. wide with 18 ft. posts. Now almost 
identical appointments inside may be provided in a build- 
ing only 75 ft. 10 in. long and 44 feet wide by placing the 
stalls in two rows on each side of a common passageway 
11.5 ft. wide, and in this arrangement only 18,709 sq. ft 
of floor and outside surface would be required as against 
21,759 sq. ft. in the structure in use, or 14 per cent. less. 



t^ 



COURT 



passage: 





GUTTER 












STALES 








STALqs 





FEED PASSAGE 




D HARNESS CASE 
S. SHOOTS 
H. HYDRANTS 




Fic/. 5. 



The storage capacity for hay would be greater in the more 
compact structure and it would be warmer and more 
cheaply ventilated. The frame of the more compact struct- 
ure would cost a little more but the total cost could not 
exceed seven-eighths that of the present form. 

Th en, again, where several buildings are made to do the 
servi ce of a single larger one there is often a still greater 
diffe rence in first cost. This difference you will more fully 
reali ze after making a direct comparison. 

He re is a group of three buildings. Fig. 6, on a dairy 
farm, more than usually compact, which provides shelter 
for 3 7 cows and 15 horses and has besides a granary 14 x 
24 ft . There is no silo and the storage capacity for feed 
is inadequate for the animals housed. Notwithstanding 



166 

these facts, the outside surface of these three buildings is 
only 269 sq. ft. less than that of this round barn, Fig. 1, 
which shelters 56 more animals, contains a 325 ton silo. 




Fig. 6. 

storage space enough for all feed, a 16 x 40 granary and 
a tool space of equal area. As indicated on this chart, 
Fig. 7, with almost the same outside exposure the single 
structure incloses a floor space exceeding that of the three 
separate buildings combined by an area 87 x 87 ft. on a 
side. 

In another group of buildings, one of which is not shown 
by a photograph, Fig. 8, shelter is provided in very much 
too cramped quarters, for 114 cows and eight horses, but 
with no tool house, and no provision for driving behind 
the cattle in cleaning. As indicated on this chart, Fig. 7, 
the outside surface of these buildings exceeds that of the 
round barn by an area 64 feet on a side while the total floor 
space is less by an area 81.5 feet square. 

Here is still another group of farm buildings, Fig. 9, 
where the extreme of wastefulness of outside lumber and 
paint has occurred. In the five of this group of nine 
buildings which are used for the same purposes as those to 



167 



Total Ouiskii Surfaces, 
J JJT89S(jft 



Jbotre J 



Euess of floor- spaa 
covered bij the 
Hound Barn 

AhoveB 



Total Floor-Space 
A 5736 3gfl. m 
B6Gie ^■ 
C 1/732'- '^ 
1)13300 ' ' 




Jooire C 
31:9 X3C3 





A 

□ 



40/55 



j6X28m^ \jox/sm 



SOBOi 
/8 



18 



/4 



36 X J4 
10 







C 



t8B(\ 



iOX30 

zo 




Fig. 7. 

which the round barn is devoted, and whose dimensions 
are indicated on this chart, Fig. 9, we have an aggregate 
floor space less by a square almost 40 ft. on a side and at 
the same time an outside area greater than that of the 
round barn by a square 140 feet on a side. That is to 
say, these five buildings, without a silo and with a smaller 
tool house and granary shelter only 8G more cows and four 
more horses, but have an outside surface to keep painted 
and exposed to the cold which will more than cover two 
round barns each furnishing fair accommodations for 98 
cows and 10 horses. 



168 




Fig. 8. 

It should be evident from this presentation that, usually, 

■(^he more farm buildings can be consolidated, and the more 

nearly equal the horizontal dimensions are made the less 

lumber is required in the construction. The square barn 

or the broad rectangular forms require less lumber than 




Fig. 9. 
the long narrow ones do for the amount of space inclosed; 
and whenever the rectangular type is to be departed from 
the perfect circle permits of a cheaper, stronger and 



169 



more convenient structure than the many sided forms do 
such as IS shown in this view, Fig. 10. " ' 




Fig. 10. 

SAVING LABOR IN THE CARE OF 




Fig. 11. 



ANIMALS. 

Looking now 
to the arrange- 
ments of the 
barn with a 
view to the 
saving of labor 
in the care of 
the stock, let 
us first study 
the one whose 
provisions for 
V e n t i 1 a t ion 
and warmth 
have been not- 
ed. In the first 
place it will be 
seen. Fig. 2, 
that there is 
stored 325 tons 
of silage at the 
center of the 
^roup of 98 
cows to be fed 
where the si- 
lage may be 
dropped into 
the basement 



170 




through this chute 
and distributed to 
the cows in the 
shortest possible 
time. As shown in 
Fig. 3 too the dry- 
fodder is so placed 
that it may be 
dropped through 
chutes directly into 
the mangers at half 
a dozen different 
points. Provision 
is also made for 
taking ground feed 
from the granary 
through feed bins 
opening at the floor 
upon which the 
cows stand, at a 
point here near the 
entrance door. 

Fig. 12. In cleaning the 

barn a double wagon or boat enters the stable here, Fig. 2, 
and passes entirely around and out again at the same point ; 
it may also pass behind the inner row of cattle around the 
silo and out again at the same door. Fig. 11 is an inte- 
rior view showing a section of the outer row of stanchions 
in this barn Fig. 12 is an interior view of the same 
barn looking toward a nearly empty hay mow to the left 
of the silo and shows how a loaded wagon may drive en- 
tirely around the silo and out again. 

It is much more difficult to make as convenient a dis- 
tribution of the feed in the rectangular type of barn or to 
arrange as nicely for the cleaning of the 'barn. It is, how- 
ever, possible to make a close approximation of these con- 
veniences as will be seen from this diagram Fig. 13, which 
shows how it may be done in barns of two sizes, one pro- 
viding for feeding 96 cows, and the other for feeding 56. 
In these plans both the silage and the dry fodder may be 
dropped directly into the mangers between the two double 
rows of cows. The cleaning also may be done with team 
and wagon or boat but three driveways and six outside 



171 

doors are required. The silo in neither of these cases can 
be permitted to reach the ground floor and hence must be 
shallower and relatively more costly in construction. It 
will be seen that the smaller barn differs from the larger 
one only by omitting two of the bents. 




;[_]/<» ■'■ci^^ J; 



;i.BAjR;N FliqOK] 






'.ZOfr DEEP 



llC^AtlVI 



56 CATTLE 



CAT Lt 





HAYMOW 
ISX60 

3 

BARN Floor 

(6A60 





GRAIN 


suo le'-je 


GRAIN 





BARN Floor 

'6X60 



HAYMOW 
(5 A 60 





SECOND FLOOR 



Fig. 13. 

In Figs. 14 and 15 are shown two views of a three-story 
barn owned by Mr. Hiram Olmstead, Walton, N. Y. , where 
the plan of construction permits driving upon each of the 
three floors. This allows both hay and silage to be unloaded 
from the upper floor where it falls by gravity into place 



172 




Fig. U. 
rather than having to be lifted, thus saving labor and 
time. A full- description of this elegant barn may be 
found in Hoard's Dairyman for May 2, 1893. 




Fig. 15. 

CONSTRUCTION OF THE SILO. 

Wherever a silo can be built cylindrical in form as shown 
in this photograph, Fig. 16, that form should be adopted as 



173 



it has been found to praserva the silage much better than 
the rectangular types and is sbroiiger and m3re cheaply 
built. The depth, if possible, never should be less than 








Fig. 16. 

24 feet and 30 feet is better than 24. Wherever the silo is to 
be built outside of a barn the rectangular type should rarely 
be adopted, as in such situations, if the necessary depth is 
provided, they are much more costly and never can preserve 
the silage as well on account of the springing of the walls 
under the great lateral pressure of the silage at first which 
inevitably admits air to the silage no matter how tight the 
walls may be. In the round silo there can be no spreading 
when built of wood, as each board is a hoop and the strain 
comes lengthwise of the grain. Except in silos having 
diameters greater than thirty feet there is no occasion for 
using studding larger than 2x4 inches, whereas nothing 
smaller than 2 x 10"s or 2 x 12's can be safely used in rect- 
angular silos unless placed inside of and partly supported 
by the walls of another building. 

Round silos may be built of wood, stone, brick or iron, 
but at the present prices of materials wood is the cheapest 
for the parts above ground. 

Where drainage will permit of it the bottom of the silo 



174 



sliould extend two to three feet below the level of the floor 
upon which the animals to be fed stand, and the stone wall 
should be 18 inches thick and extend 12 inches above the 
level of the ground outside to protect the woodwork from 
decay. 

This view, Fig. 17. shows the method of constructing 
the walls of a round silo. The upper 8 inches of the 
foundation wall should be beveled back to a thickness of 
about 8 inches as shown here and should be thoroughly 




Fig, 17. 

Showing the coDstruction of all wood round silo. Sills 2 x4's cut in sections on a 
radius of the silo circle, bedded in i-iortar and toe-nailed tof^ether. Plates the 
same, , spiked to top of itludding. Stuading JJx4's one fo^.t apart. Short lengths 
may be used, la:>peu. to get the depth. 16"s and 14's will give a silo 30 feet deep. 
Lining made Jrom fencing ripoed in two. Outside sheeting the same. Siding for 
silos under .30 feet, outside diametar, common ' siding rabbeted; for silos 
more than 28 feet, ouiside diameter, common drop siding or ship lap may be used. 
A, shows ventilators between studding. Auger holes are bnred at bottom between 
studding, and the boards lack two inches of reaching plate at top, inside Both 
sets of opening- are covered with wire cloth to keep out vermin. There should be 
a line of feeding doors from top to bottom, each 2 or 3 teet by 5 feet, and about 2.5 
feet apart. 

plastered with two coats of good cement to render it air- 
tight, this being put on, however, after the silo is other- 
wise completed in order to make the joint between the sill 
and the w^all perfectly air-tight. Silage juices tend to 



175 

soften the best of cements and render them porous ; to pre- 
vent this it is a good plan to apply a good coat of white- 
wash each year, this being found in practice to about neu- 
tralize all of the acid which comes to the wall, and thus 
protects it. 

To prevent rats from burrowing under the wall and ad- 
mitting air to the silage, it has oeen found desirable to 
cover the bottom of the silo with a thick coat of grout as 
tshown here. 

The walls of the silo above the stone work may usually 
be built of 2 X 4 studding set one foot apart and- covered 
inside with two or three thicknesses of half-inch boards 
made from good fencing, sized to a uniform width, and 
then split in two, the layers having a good quality of tar 
paper between, as shown at this point (Fig. 17). Outside 
there should be, in cold climates, another layer of the same 
half-inch lumber and this covered with paper and finally 
with ordinary beveled siding having the thick edge rab- 
beted as shown in the fig-ure here. 

To prevent the lining and studding from rotting ample 
ventilation must be provided and this may be done by bor- 
ing holes through the siding just above the sills between 
each pair of studs and covering them with wire netting to 
keep out vermin as indicated. Fig. 17. At the top the 
lining should not quite reach the plate, thus providing a 
place for the air which enters below to escape, to keep the 
lining dry. The openings of the silo should also be 
guarded by netting to prevent silage from falling in be- 
hind during filling. 

The sills and plates are made by sawing 2 x -Is in two 
foot lengths on a bevel so that they will lie togfether in a 
circle. The pieces which form the sill are toe-nailed to- 
gether and bedded in mortar on the wall, while the pieces 
for the plate are spiked down upon the tops of the stud- 
ding. Only one thickness is required in either case. 

The roof can best be built in conical form and covered 
either with shingles or a good quality of roofing felt. If cov- 
ered with the latter, the felt will be cut into leoo-ths de- 
termined by the slant height of the roof and these pieces 
will then be cut in two diagonally lengthwise, running the 
strips up and down on the roof lapping about four inches. 

The roof boards may be put on in the manner shown in 
Fig. 18, which shows the underside of the roof of a silo IG 



176 



feet in diameter. This is a circle five feet in diameter 
made of two thicknesses of two inch stuff spiked together. 

The roof boards are 
pieces of fencing 
sawed to the length 
of the slant height 
of the roof and then 
ripped in two di- 
agonally at the 
mill. After fixing 
the circle in place 
the roof boards are 
nailed directly to 
it and to the plate 
when the wdiole be- 
comes self-support- 
ing. 

For larger silos 
two or more circles 
may be used and 
the roof made with- 
out rafters in the 
same way. 

Every silo roof 
should be provided 
Fig. 18. wdth , a ventilator 

This may be an ordinary cupola or it may be made of gal- 
vanized iron, as shown in Fig. 16, and provided with a 
damper to be closed during cold weather to protect the 
silage from freezing. The ventilator is necessary in order 
to insure a rapid drying of the w^alls and inside of the 
lining as fast as the silage is removed so as to avoid de- 
cay. 

The feeding doors should form a series one above the 
other placed about three feet apart as shown in Fig. 16. 
They should be about two feet wide and three and one-half 
to four feet high. The doors may be made and hung as 
shown in Fig. 19. Here there are three thicknesses of 
matched flooring with two layers of tar paper betw^een 
nailed to the tw^o cleats. Each door swings on a pair of 
six-inch T hinges, and is fastened shut by two strips of 
band iron bolted to the cleats and shutting down over two 
half inch bolts reaching through the wall of the silo at 




177 



these points and provided with handle burrs like those upon 
the rods to the end boards of wagons. 

For silos less than 20 feet in diameter these cleats should 
be cut to the curvature of the silo and the door made of 




Fig. 19. 

four-inch flooring with paper between, as in the case just 
described. This avoids the shoulder formed by the flat 
door. 

When the doors are closed for filling, the leakage of air 
about the doors may be prevented by tacking over the 
joints, on the inside, strips of tar paper about six inches 
wide, letting the silage come directly against these strips, 
which^are^of course replaced each year. 



Table for Determining the Relative 






40 



41 



42 



43 



44 



45 



37 
44 
52 
59" 
68 
76 
84 
92 



31 
38 
46 
53 
CO 
68 
76 
84 
92 



26 
33 
40 

47 
54 
61 
69 

77 
84 
92 



21 
28 
34 
41 

48 
55 



38 62 

39 70 



40 
41 
42 

"32" 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
13 

"32" 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 



77 
85 
92 

16 
23 
29 
36 
43 
49 
56 
63 
70 
78 
85 
92 

12" 
18 
24 
31 
37 
44 
50 
57 
64 
71 
78 
85 
92 



® 3 



Xi 



46 



47 



48 



49 



50 



33 
34 

35 

36 
37 
38 
39 
40 
41 
42 
43 
44 
45 



34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 



35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 



36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 



37 
38 
39 
40 
41 
42 
4;3 
44 
45 
46 
47 
48 
49 



®^ 


j£i 


;q 


(D^ 


^ 


,6 
72 


a.h? 


XJ 


j£ 


«>» 


•I2 


,D 


3 




s 
,0 


5 


■^§ 


B 


3 

^ 


5s 


^a 


1 >. 


■s 


SB 


>. 


-b3 


SB 


■ h 


■M 


■SS 


03^ 
14 




38 


22 




43 


30 


Q 


48 


35 








20 


1 


39 


28 




44 


34 




49 


40 


26 




40 


33 




45 


39 




50 


44 


82 




41 


39 




46 


44 




51 


49 


38 




42 


45 




47 


50 




52 


54 


45 




48 


50 




48 


55 




53 


58 


51 


51 


44 


56 


50 


49 


60 


61 


54 


63 


58 




45 


62 




50 


65 




55 


68 


65 




46 


68 




51 


71 




56 


73 


72 




47 


74 




52 


77 




57 


78 


79 




48 


81 




53 


82 




58 


84 


85 


1 


49 


87 




54 


88 




59 


81 


93 


— — 


50 . 
39 


93 
24 




55 

IT 


94 
31 




60 
49 


94 
37 






22 




40 


29 




45 


36 




50 


41 


28 




41 


35 




46 


40 




51 


45 


34 




42 


40 




47 


45 




52 


50 


40 




43 


46 




48 


50 




53 


54 


46 




44 


51 




49 


55 




54 


59 


52 


52 


45 


57 


57 


50 


61 


62 


55 


64 


59 




46 


63 




51 


66 




56 


69 


66 




47 


69 




52 


71 




57 


74 


72 




4H 


75 




53 


t t 




58 


79 


79 




49 


81 




54 


83 




59 


84 


86 




50 


87 


' 


55 


88 




60 


89 


93 

18 




51 
40 


94 
25 





56 
45 


94 
32 





61 
50 


95 
38 




23 




41 


31 




46 


37 




51 


42 


29 




42 


36 




47 


42 




52 


46 


35 




43 


41 




48 


46 




53 


51 


41 




44 


47 




49 


51 




54 


55 


47 




45 


52 




50 


56 




55 


60 


53 


58 


46 


58 


5S 


51 


61 


63 


56 


64 


60 




47 


63 




52 


67 




57 


69 


66 




48 


69 




53 


72 




58 


74 


73 




49 


75 




54 


78 




59 


79 


79 




50 


81 




55 


83 




60 


84 


86 




51 


87 




56 


89 




61 


89 


93 
19~ 





52 

41 


94 

27 




57 

46 


94 
33 




62 
51 


95 
38 






21 




42 


32 




47 


38 




52 


43 


30 




43 


37 




48 


43 




53 


47 


36 




44 


42 




49 


47 




54 


51 


42 




45 


48 




50 


52 




55 


56 


48 




46 


53 




51 


57 




56 


60 


54 


54 


47 


59 


59 


52 


62 


64 


57 


65 


60 




48 


64 




53 


67 




58 


70 


67 




49 


70 




54 


72 




59 


74 


73 




50 


76 




55 


78 




60 


79 


80 




51 


82 




56 


83 




61 


85 


86 




52 


88 




57 


89 




62 


90 


93 
21 




53 
42 


94 

28 


L- 


58 
47 


94 
34 




63 

52 


95 
39 






26 




43 


33 




48 


39 




5;^ 


44 


32 




44 


38 




49 


44 




54 


48 


37 




45 


48 




50 


48 




55 


52 


43 




46 


49 




51 


53 




56 


56 


49 




47 


54 




52 


58 




57 


61 


55 


55 


48 


59 


m 


53 


68 


65 


58 


65 


61 




49 


65 




54 


68 




59 


70 


67 




50 


70 




55 


73 




60 


75 


74 




51 


76 




56 


78 




61 


80 


80 




52 


82 




57 


84 




62 


85 


87 




53 


88 




58 


89 




63 


90 


93 




54 


94 




59 


94 




64 


95 



Directions: Notice the table is in three-column sections. Find air tempera 
ion. In third column opposite this is relative humidity. Example: Air tempera 
site 53° is 63, which is the per cent, of saturation. 



Humidity in the Air of Curing Rooins. 



1 








53 


40 






54 


45 




55 


49 




56 


53 




57 


57 




58 


61 


<>(> 


59 


66 




60 


71 




61 


75 




62 


80 




63 


85 




U 


90 




65 

54 


95 
41 






55 


45 




56 


49 




57 


53 




58 


58 




5J/ 


62 


67 


60 


66 




61 


71 




62 


76 




63 


80 




64 


85 




05 


90 




66 


95 




55 


42 






56 


46 




57 


50 




58 


54 




59 


58 




60 


63 


68 


61 


67 




62 


71 




63 


76 




64 


81 




65 


85 




66 


90 




67 


95 





56 


43 




57 


47 




58 


51 




59 


55 




60 


59 


69 


61 


63 




62 


67 




63 


72 




64 


76 




65 


81 




66 


86 




67 


90 




68 
'ST 


95 
44 






58 


48 




59 


52 




60 


55 




61 


60 




62 


64 


70 


63 


68 




64 


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69 
73 
76 
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88 
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96 



71 I 53 

72 I 56 



59 
63 
66 
69 
73 
78 77 
80 

80 84 

81 88 

82 92 

83 96 



53 
56 
60 
63 
66 
70 
73 
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96 


74 


54 


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57 


76 


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64 


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67 


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74 


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82 


81 


83 


84 


84 


88 


85 


92 


86 


96 


75 


55 


76 


58 


77 


61 


78 


64 


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67 


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71 


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83 


81 


84 


85 


85 


88 


86 


92 


87 


86 


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55 


77 


58 


78 


61 


79 


64 


80 


68 


81 


71 


82 


74 


83 


78 


81 


81 


85 


85 


86 


88 


87 


92 


88 


96 


77 


56 


78 


59 


79 


62 


80 


65 


81 


68 


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84 


78 


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96 



ure in first column, then find wet bulb temperature in second column, same divis- 
ture is 60° in first column; wet bulb isSS" ia second column, same division. Oppo- 



INDEX. 



Acme harrow, 139. 

Adhesion, 7. 

Advantage of a warm soil, 123. 

Aeration of soil, need of, 93; methods 
of, 95. 

Affinity, chemical, 8. 

Air, humidity of for curing rooms, 178: 
warmed by snow storms, 77; once 
breathed unfit for respiration, 158; 
respired heavier than pure, 162; 
amount used by horse, sheep, steer, 
158. 

Air chamber, function of in pumps, 58. 

Animals, locomoi ion of, 21; bad effects 
of rain and snow on, 75. 

Animal temperatures, regulation of, 74. 

Atmosphere, transparency to ether 
waves, 67. 

Atmospheric pressure, 55; variations in, 
56; effect of variations on soil-water, 
56; on soil ventilation, 56, 149; action 
in suction pumps. 57. 

Axle, wheel and, 23; trains of wheels 
and, 23. 

Baboock and Beimling milk tests. 12; 

Baker, Prof., on effect of drainage on 
crops, 143. 

Barns, construction of, 157; need for 
right temperature in, 159; economy in 
cost, 164; saving of labor in caring for 
animals, 169. 

Beams, safe load for, 45. 

Beam-wheel, effect on draft of plow, 133. 

Belting, 36; activity of, 36. 

Bins, pressure of grain in, 52 

Bodies, structure of , 5. 

Breaking, strength of wood, 42; con- 
stants of materials, 43; load, 44, 45. 

Building, economy in cost. 164. 

Burning green or wet wood, 77. 

Capacity of soil to store water, 105; ef- 
fect of manure on, 118. 

Capillary action, 47. 

Capillary movement of water in soil, 
rate of, 110. 

Cement in silos, 174, 

Centigrade degrees reduced to Fahren- 
heit. 70. 

Centrifugal force, 12; to compute, 13; 
creaming, 13. 

Centrifuges, speed of, 24. 

Chamberlin and Salisbury, size of soil 
particles, 93; composition of subsoils, 
91. 

Cheese curing rooms, humidity in, 178. 

Chemical, changes, 3; waves. 65; afiftn- 
ity, 8. 

Chimneys, draught in, 67. 



Churn, friction in, 37. 

Cohesion, 7. 

Cohesive sti'ength of timber, 39; of other 
materials, 39. 

Composition of subsoils, 91. 

Conduction of heat, 66. 

Conductors and non-conductors of elec- 
tricity, 81. 

Constants, breaking, 42,43. 

Conservation of soil water, 120,121, 

Construction of a silo, 172; of fai'm build- 
ings, 157. 

Control, of water content of soils. 119; 
of moisture by firming the ground, 122; 
of soil temperature, 124. 

Convection of soil, 87. 

Cooling milk, 75. 

Coulters, effect on draft of plows, 134. 

Creaming, gravity method, 12; centrifu- 
gal, 13; force, 14. 

Crooks, motion of molecules, 6. 

Cultivation, influence on evaporation, 
12,; flat, 122: deep and shallow, effect 
on soil temperature, 126. 

Cultivators, objects of, 140. 

Curing rooms, table of humidity for, 
178. 

Deep and shallow cultivation, effect on 
soil temperature, 126; effect on soil 
moisture, 122, 126. 

Deep tillage to increase evaporation, 122. 

DeiJth, of root feeding, 104; of silo, 173; 
of drains, 152. 

Diffusion, 5, 48. 

Digestion, more oxvgen needed during, 
159. 

Dirt in journals, bad effect of, 36. 

Disc harrow, 138. 

Ditches, open for drainage of land, 142. 

Doors of siio, 176. 177 

Draft, of plow. 132: effect of beam wheel 
on, 133; of sulky plows. 134: effect of 
coulters on, 134: on common roads, 25; 
on uneven roads, 27; of horse, 25; on 
up-gradee, 26; with wide and narrow 
tires. 28. 

Drains, best depth for, 152; best distance 
between, 1.52; grade of, 154; outlet of, 
155; junction tile in, 1.55; obstructions 
to, 155; mains and laterals, 155. 

Drainage, farm. 142: in Illinois. 142; ne- 
cessity for, 143; influence on soil tem- 
perature, 145; on soil ventilatiori, 95, 
148: increases available water, 149; lands 
likely to be benefited by, 150; road, 30. 

Draught in chimneys, 67. 

Earth-worms, in soil formation. 86; in'soil 
aeration, 95; in soil convection, 87. 



182 



Economj\ in cost of farm buildings, 164; 
in labor of caring: for animals, liid. 

Electrical induction, 80. 

Electricity, nature of, 79; atmospheric, 
80; positive and neKative, 81 ; discharges 
from a point, 81; conductors and non- 
conductors of, 81 . 

EUiott, C. G., tile drains, 156. 

Energy, 10; and matter indestructible, 
10; temperature a measure of. 68; lost, 
sliding iriction in machinery, 36; stor- 
ing of, 15. 

Energy, solar, how reaches the earth, 
63; mechanical value of, 64, 65. 

Ether waves, kinds of, 64; work done by, 
65; transparency to, 67. 

Evaporation, cooling effects of , 73; heat 
units required for, 73; loss of water by 
surface, 112; influence of cultivation 
on, 120, 121; of topography on, 113; of 
woodlands on, 115; deep tillage to in- 
crease, 122; surface tillage to check, 
120. 

Evener, two horses, 18; givmg one horse 
the advantagt", 19 . 

Fahrenheit degrees reduced to centi- 
grade, 70. 

Farm drainage, 142. 

Fences, wire, danger of lightning from, 
83. , . 

Ferment, germs producing natural ni- 
trates, 94. 

Firming soil to control moisture, 121. 

Floating gardens of the Chinese, 94. 

Flotation, principle of, 53. 

Flow, of water, 60; velocity of discharge 
from pipes, 61 ; of air through venti- 
lfl.tors IG'i 

Fluids, 46; pressure of, 50: sp. gr. of, 55. 

Foot-pounds, 9. 

Force, kinds of, 6; matter and, 3; cen- 
trifugal. 12; to compute centrifugal, 
13; sti-ength of creaming, 14. 

Forces, molecular, 7. 

Friction, between solids, 34 ; influence of 
pressure on, 35; between solids and 
liquids, 35: of rest or static, 34; of mo- 
tion or kinetic, 35; sliding, 36; in the 
churn, 37. 

Gaseous state, 9 . 

Germination, best temperature for, 124, 
144; oxygen essential to, 93, 147. 

Glacial subsoils, 91. 

Grade of drains, 154. 

Grain in bins, pressure of, 52. 

Gravitation, 7. 

Gravity, method of creaming, 12; spe- 
cific, 53. 

Green and wet wood, burning, 77. 

Ground-water, contour map of surface, 
99; and wells, 100: effect of pu.mping 
on, 100: fluctuations in level of, 103; 
best height of, 104; surface of after 
I'ain, 153, 154. 

Grout, to keep rats out of silo, 175. 

Haberlandt, best temperature for ger- 
mination. 124, 144. 

Harrow, uses of, 138; .\cme, 139; Disc, 

138; tooth, 140. 
Head of water, 61 . 

Heat, nature of, 63: waves 65; transfer of, 
66; unit, 70; units required to melt ice. 



73, 75; evaporate water. 73, 75; latent, 
72; specific, 70; of soils, 71. 
Hellriegel, amount of water used by 
plants in Prussia. 96; best proportion of 
soil saturation, 108. 
Horse power, 9 . 
Horse, giving one the advantage, 19; 

traction power of, 25. 
Hot-beds, principle of construction, 68. 
Humidity of air in curing I'oom.s, table 

of, 178. 
Hydrogen molecules, distance traveled 

without collision, 6. 
Ice, heat units required to melt, 73, 75; 
cooling milk with, 75; action in soil 
formation. 85. 
Illinois, drainage in, 142; yield of grain 

increased by drainage, 142. 
Inclined plane, 24. 
Inertia, 11. 

Irrigation, natural sub-, 151. 
Journals, du't in. 36. 
Junction tile, 155. 
Kinetic friction, 35. 
Klenze, water capacity of different soils, 

105. 
Lactometer, 48, 55. 
Landside of plow, function of , 131. 
Lands likely to be benefited by drainage, 

150. 
Latent heat, 72. 
Level of ground water, fluctuations in, 

103. 
Lever, 16. 

Lightning, protection against. 80, 82; 

when an object may be struck by, 81; 

danger of from wire fences, 83; rods, 

functions of, i<2; essential features, 82. 

Light waves, 65. 

Liquids, ideal, 8; surface tension of, 46; 
specific gravity of, 55; osmose of, 49; 
solution of solids in, 48; pressure of in 
vessels, 51; and solids, friction be- 
tween, 35. 
Load, breaking, 44, 45; safe for horizon- 
tal beams. 45; for posts, 39. 
Locomotion of animals, 21. 
Loss of water by surface evaporation, 

112. 
Lumpy soil, bad effects of, 119; effect on 

temperature, 125. 
Macadam system of road construc- 
tion, 29. 
Machines, elements of, 16; not genera- 
tors of energy, 11. 
Manure, depth of plowing in, 117; effect 

on water capacity of soil;*, 118. 
Map, contour, of ground water surface, 

99; of area occupied by wells. 98. 
Materials, strength of , 38, :39, 42, 43 
Matter, kinds of, 3; constitution of, 4; 
inertia of, 11: indestructible, 10; and 
force, 3. 
Mechanical powers, 16. 
Melting of ice and snow, 73, 75. 
Milk, test, 12; coolmg with ice and cold 
water, 75; production, effect of venti- 
lation on, 159. 
Molecular forces, 7. 

Molecules. 4; size of, 4; properties of, 5; 
of bodies not at rest, 5: of hydrogen, 
distance ti-aveled without collision, 6. 



183 



94, 
147; 

by 
159; 



Momentum, 15. 

Morin, Gen., experiments concerning 
traction on roads, 31. 

Morton, on draft of plows, 133. 

Mulches, effect of thin soil, 1*21. 

Muscle, force of triceps and biceps, 21. 

Natural sub-irrisation, 151. 

Nitrates, natural, 94. 

Nitric ferment, 94; best temperature for, 
124, 144; need of oxygen for, 94, 148. 

Obstructions to drains, 155. 

Oil, use of in machines, 35. 

Organic matter, plowing in, 117. 

Osmosis, 49. 

Outlet of drains, 155. 

Oxygen, essential to nitrification, 
148; essential to germination, 93 
amount required by animals. 158; 
man, 159- during digestion, 
amount varies with temperature, 160; 
uses in soil, 93, 147. 

Percolation of impure water into wells, 
101; rate of in field soil 109; influence 
of topography on, 112; from long col- 
umns of sand, lOti . 

Pillars, strength of pine, 38. 

Pipes, flow of water in, 61. 

Piston, size of, 57. 

Plane, inclined, 24. 

Plants, amount of water consumed by. 
96, 97; proportion of soil- water avail- 
able to, 106. 

Plow, work done by, 127; mechanical 
prin jiples of, 130; advantage of oblique 
cutting edges, 130; function of land- 
side, 131; proper line of draft of, 131; 
draft of in different soils, 132; effect of 
beam- wheel on draft, 133; effect of 
coulter ou di-aft of, 134; sulky, draft 
of, 134; scouring of, 135; pulverizing 
function of, 135; care of, 136; subsoil, 
137. 

Plowing, early, saving of soil moisture 
by, 113, 120; in of organic matter, 117; 
depth of plowing in of manure, 117. 

Pounds, foot-, 9. 

Power, exertion of great, 24; horse 
traction, of a horse, 25; sweep, 
tread, 2">. 

Powers, mechanical. 16. 

Pressure, atmospheric. 55; of fluids, 
of liquids in vessels, 51; of grain 
bins, 52 

Puddled soils, 123. 

Pulley, 31; horse-fork and, 33; used 
raise stones, 33. 

Pump, suction, 57. 

Pumping, rate of, 58; from wells, effect 
on ground-water surface, 100. 

Pupey, on draft of plows, 132. 

Radiation, 64. 

Rafters, breaking load of, 45. 

Rain and snow on domestic animals, ef- 
fects of, 75; inches per ton of dry mat- 
ter of crops, 97 . 

Rats in silos, to prevent, 175. 

Roads, construction. Macadam system, 
29; Telford system, 29; drainage of, 
30; draft on,' 25; good, make high 
grades more objectionable, 27: Gen. 
Morin's experiments on draft on, 31; 
soft and uneven, 27. 



, 9; 
24; 



50; 
in 



to 



Rod, lightning, functions and features 
of, 82. 

Roller, effects of, 122, 141. 

Roof of silo, 175; ventilator for, 176. 

Root, breathing, 94 ; feeding, vertical ex- 
tent of, 104; room, how drainage in- 
creases, 149. 

Roots o trees obstruct drains, 155. 

Sachs, plants wilting with low tempera- 
ture, "144. 

Sandborn, Prof. .T. W., draft of plows, 
133; coulters, 134. 

Scales, platform, 20. 

Screw, 34. 

Seed bed, rolling, 123. 

Seeds, germination of, best temperature 
for, 124, 144; oxygen essential for, 93, 
147. 

Sheep, ventilation of barns for, 162. 164. 

Silage, lateral pressure of, 173; juices 
soften cement, 175. 

Sills and plates of silo, 175. 

Silo, cement in, 174; doors. 176; best 
depth, 173; round, 17-3, 174; construc- 
tion of, 172; roof of, 175; sills and 
plates, 175; size of studding needed in, 
173; springing of walls of x-ectaug- 
ular, 173; stone wall in, 174. 

Siphon, 60. 

Sliding friction in machinery, 36. 

Snow, heat required to nielt, 75, 76; 
storms warm the air, 77. 

Soil, capacity to store water, 105; effect 
of manure ou capacity to store water, 
118: advantages of warm, 123, 144; 
moisture, Junctions of, 96; drainage, 
need for, 143; needs of aeration, 93; 
methods of aeration, 95; breathing, 56; 
149; convection, 87; cooling of by 
evaporation, 73. 146; nature and origin, 
84: particles, size of, 92; removal, 88; 
surface, 88; kinds of, 89; kinds which' 
yield their moisture to plants most 
completely, 108; puddled, 123; capillary 
movement of water in, 110; control of 
water content, 119. 

Soils, specific heat of, 71 . 

Soil temperature, best, 124; control of, 
124; effect of deep and shallow cultiva- 
tion on, 126; effect of rolling on, 124, 
125: effect of drainage on, 125, 145. 

Soil-water, conservation of, 120, 121 ; ef- 
fect of atmospheric pressure on, 56; 
influence of cultivation on evaporation 
of, 121: movements of . 109; proportion 
of available to plants, 106; transloca- 
tion of , 111. 

Solar energy, 63; mechanical value of, 
64, 65; work done by, 65. 

Solids, friction between, 34; influence of 
press ire on friction between, 35; solu- 
tion in liciuids, 48. 

Solution, 48. 

Specific gravity, 53; to find, 53, 55; table 
of, 54. 

Specific heat, 70; of soils, 71. 

Speed of centrifuges, 24. 

Steam, latent heat of , 73. 

Strength, of creaming force, 14; of ma- 
terials, 38, 42,4^3; ot pillai-s,38; tensile, 
of timbers, 39; tensile of other materi- 
als, 39; transverse, of timbers, 41 ; trans- 



184 



verse, principles of. 39; of surface ten- 
sion, 4t). 

Stress, kinds of, 38. 

Studding, size needed in silos, 173. 

Sub-soil, 90; variation in composition of, 
91. 

Sub-soil plow, 137; use of. 137. 

Sub-irrigation, natural, 151. 

Substances, states of, 8. 

Suction pump, 57. 

Sulky plow, draft of, 134. 

Surface tension, 46; strength, of, 46; in- 
fluence on lactometer readings, 48. 

Sweep horse-power, 24 . 

Table, traction on roads, 2o; breaking 
load of rectangular pillars, 39; tensile 
strength, 39; breaking constants, 43; 
safe loads for beams, 45; water press- 
ure, 51; specific gravities, 54; specific 
heat of soils, 71: water j^er lb. of dry 
matter, 95, 97; capacity of soil to 
store water, 106; draft of plows, 133; 
soil temperatures, 145; relative humid- 
ities, 178. 

Telephone, 79. 

Telford system of road construction, 29. 

Temperature, amount of oxygen used 
varies with, 160; best for germination, 
124, 144; best for nitric ferment, 124, 
144; control of, 124: effect of rolling up- 
on m soil, 124: effect of deep and shal- 
low cultivation upon, 126; influence of 
drainage on in soil, 125, 145; need for 
right, in barns, 159; measurement of, 
68; regulation of in animals, 74; 

Thermometer, testing a, 69; kinds of 
scales, 70; wet bulb, 74; 

Tile, best depth, 152; best distance, 152; 
grade of , 154; mains and laterals, 155; 
outlet of, 155; obstructions to, 155; 
junction, 155 

Tillage, objects of, 116; implements of. 
127: deep to increase evaporation, 122; 
surface to check evaporation, 120. 

Tilth, importance of good, 118. 

Timbers, strengtU of , 39, 41. 

Tires, wide and narrow, 2ii. 



Topography, influence upon evapora- 
tion, 113; influence upon percolation, 
112. 

Traction, on common roads, 25; power 
of a horse, 25; increased speed dimini- 
shes power, 26; power diminished by 
up-grades, 26; Gen. Morin's experi- 
ments in France, 31 

Translocation of soil water, 111. 

Tread power, 25. 

Tree roots obstruct drains, 155. 

Unit of heat, 70. 

Velocity of flow, of water in pipes, 61, 
62; of air in ventilator, 162. 

Ventilating flues, capacity of, 162, 159; 
for sheep barns, 162; for silo, 176. 

Ventilation, of barns, 160; correct 
method, 162; faulty method, 162: of 
round barn, 162; need for, 157; effect 
on milk production, 159; of silo, needed, 
176. 

Ventilation of soil, needed, 93; influence 
oc drainage on, 95, 148. 

Viscosity, 49. 

Wagon tires, wide and narrow. 28. 

Water, head of. 6' ; flow of in pipes, 60, 
61; consimied by plants, amount of, 
96 , 97 ; impure percolating ihto wells, 101 ; 
capacity of soil to store, 105 ; rate of per- 
colation of, 109; loss of by surface 
evaporation, 112; control of in sod, 119, 

Water, capacity on soils, 105; effect of 
manure on, 118. 

Water-table, position and attitude of, 97; 
fluctuation in level of , 103; best height 
of, 104 

Waves, ether, kinds of, 64. 

Weeds, importance of destruction of, 
116. 

Wells, and ground- water, 100; lowering 
of water in, 101; percolatoin of impure 
water into, 101. 

Wheel and axle, 23; trains of, 23. 

Wind, effect on evaporation, 115. 

Wire fences, danger of lightning from, 
83. 

Woodlands, effect on evaporation, 115. 

Work, 9; done by either waves, 65. 



i 




«8Jl^ 





